So we can understand from this there there are two separate instructions (i) for ekadasi (ii) for Gaura Purnima and Janmastami.
"you can offer ekadasi to Lord Caitanya who acts as a devotee, but not to Krsna."(Bhanu Swami. 5th March 1999. [Text 2136851 from COM] )
"So far the Advent Day of Lord Caitanya is concerned, I have written a full suggestion to Montreal, in which the main points are that we should all observe strict fasting up till moonrise, and at that time, an offering is made to Lord Caitanya of Ekadasi foods, fruits, peanuts, milk, and so forth. Then, on the next day, Friday the 15th, a full-scale feast is held to celebrate His Advent Day. On the 14th, chanting, reading of Srila Bhaktivinode's book, Life and Precepts and Caitanya Caritamrta, Introduction to Bhagavatam, may be held all the day in the Temple." (San Francisco, written 12th March 1968 letter to Balai)
"The injunction to fast on Ekädasi is especially meant for devotees; on Ekädasi there are no restrictions regarding food that may be offered to the Lord. Lord Sri Caitanya Mahäprabhu took the food of Lord Vishnu in His ecstasy as vishnu-tattva".(CC Adi-lila 10:71 purport.)
"Lord Caitanya's Appearance day falls on March 22 (1970), that is on a Sunday. The devotees should fast until evening, when there is a ceremony and offering of a small amount of Ekadasi preparations. The next day, the devotees should celebrate amongst themselves with a small scale feast. You may hold the celebration open to the public on the following Sunday. The preparation to be offered specially on this occasion is bhuni kichri: Fry equal parts dal and rice in ghee and massala. Add two times water as dal and rice, and add vegetables (if you use more ghee, use less water). Cook it until it is dried and the rice is soft."(Letter to Krishna dasa. 18th February 1970. Los Angeles.)
"P.S. No feasting in the evening of Caitanya's birthday. Fasting all day till evening moon rise. Then take Prasadam like Ekadasi. Next day you can have full swing feasting. On the birthday if can take a procession of Kirtana on the street it is very nice." (Post Script to Letter to Rayarama dasa. September. Unknown place unknown date Ref:91-05-14.)
There is an amusing discription of the first ISKCON janmastami "feast" as described by Hayagriva Prabhu in his biography "Hare Krishna Explosion pg 62" He writes:"as midnight approaches, we hungrily envision the great birthday feast of Lord Krishna, mountains of succulent prasadam: cake and kachoris, halava and puris, sabji, sweet rice, samosas and gulabjamuns. Just a few minutes before midnight, Swamiji finally descends from his kitchen with the Prasadam. But our faces drop. There is only a platter of cut fruit."
There is a discription of Gaura Purnima in Mayapur India 1976 from the biography "A Transcendental Diary" Vol1 Mar.16. by Hari Sauri Prabhu: pg.461. "GAURA PURNIMA. The Appearance day of Sri Caitanya Mahaprabhu. Everyone fasted until moon rise and then took an Ekadasi feast, although Prabhupada said this was not compulsory.
Pg.466: "Many Devotees sold copies of the Gitar-gana, and mass distribution of Halava prasadam went on throughout the day."
Pg.469 "At one point Prabhupada sent me out to see how many visitors had come , and he was very happy to hear of the large crowds. Typically, he wanted assurance that prasadam was being distributed to all."
"The Caitanya-bhägavata, Ädi-lilä, Chapter Six, fully describes the Lordís accepting vishnu-prasäda on the Ekädasi day at the house of Jagadisha and Hiranya. Regular prasäda is offered to Lord Vishnu on Ekädasi because, while fasting is recommended for devotees on Ekädasi, it is not recommended for Lord Vishnu. Once on Ekädasi in the house of Jagadisha and Hiranya Pandita there were arrangements for preparing special prasäda for Lord Vishnu, and Lord Caitanya Mahäprabhu asked His father to go there to ask for the vishnu-prasäda because He was feeling sick. The house of Jagadisha and Hiranya Pandita was situated about two miles from the house of Jagannätha Mishra. Therefore when Jagannätha Mishra, on the request of Shri Caitanya Mahäprabhu, came to ask Jagadisha and Hiranya for the prasäda, they were a little astonished. How could the boy understand that special prasäda was being prepared for Lord Vishnu? They immediately concluded that the boy Nimäi must have supernatural mystic power. Otherwise how could He understand that they were preparing special prasäda? Therefore they immediately sent the food to Lord Caitanya Mahäprabhu through His father, Jagannätha Mishra. Nimäi was feeling sick, but immediately after eating the vishnu-prasäda He was cured, and He also distributed the prasäda among His playmates." (CC Adi-lila 14:39. purport)
The special Lila-vichitra pastimes of the Lord which are EXTRAORDINARY and not to be imitated.
If I may pose a question "If the Supreme Personality of Godhead came to you on ekadasi and gave you grains to eat what would you do???"
I for one would eat them right there on the spot, directly from the Lord's hand. Despite everything else, knowing who we are to take shelter of, just like His playmates did. (unfortunately it appears I will have to wait some time to test this case)
Adjusting the program for preaching (feasting):
"You can take quotations from the above mentioned books, and have discussions.
Fasting should be continued up to evening, then you may have food like on Ekadasi, fruits, milk, etc. On the next day you may observe festival. Janardana consulted me and said he thinks Sunday feasting would be best, so you may do that if you like. Or you may do both days, as you feel best."(Letter to Mahapurush. 7th March 1968. Regarding Gaura Purnima)
"We performed Lord Caitanya's Birthday ceremony, not very gorgeously, but amongst ourselves, and Govinda dasi cooked very nice Ekadasi foodstuffs. The next day I expected some big ceremony but it couldn't be performed. (Letter to Purusottam. 6th March 1969. Hawaii)
Fasting FOR EKADASI:
"From the very beginning of His childhood life Shri Caitanya Mahäprabhu introduced the system of observing a fast on the Ekädasi day. In the Bhakti-sandarbha, by Shrila Jiva Gosvämi, there is a quotation from the Skanda Puräna admonishing that a person who eats grains on Ekädasi becomes a murderer of his mother, father, brother and spiritual master, and even if he is elevated to a Vaikuntha planet, he falls down. On Ekädasi, everything is cooked for Vishnu, including regular grains and dahi, but it is enjoined that a Vaishnava should not even take vishnu-prasäda on Ekädasi. It is said that a Vaishnava does not accept anything eatable that is not offered to Lord Vishnu, but on Ekädasi a Vaishnava should not touch even mahä-prasäda offered to Vishnu, although such prasäda may be kept for being eaten the next day. It is strictly forbidden for one to accept any kind of grain on Ekädasi, even if it is offered to Lord Vishnu." ( CC Adi-lia 15:19. purport.)
"Mother Saci said, ďYou have spoken very nicely. I shall not eat grains
on Ekädasi.Ē From that day, she began to observe fasting on Ekädasi."(CC
Adi-lila 15:10 text.)
"It is a prejudice amongst smärta-brähmanas that a widow must observe fasting on Ekädasi but a woman who has her husband should not. It appears that before the request of Lord Caitanya Sacimätä was not observing Ekädasi because of her being sa-dhava, which means that her husband was living. Shri Caitanya Mahäprabhu, however, introduced the system that a woman, even if not a widow, must observe the Ekädasi day and must not touch any kind of grains, even those offered to the Deity of Vishnu".(CC Adi-lia 15:10 purport.)
"Shri Caitanya Mahäprabhuís pastime of fainting after eating betel nuts is a solid instruction to all of us that one should not touch betel nuts, even those offered to Vishnu, just as one should not touch grains on the Ekädasi day. Of course, Lord Caitanya Mahäprabhuís fainting had a particular purpose. As the Supreme Personality of Godhead, He can do whatever He likes and eat whatever He wants, but we should not imitate His pastimes." (CC Adi-lia 15:16 purport.)
"Devotee: On ekädasi, we can offer the Deity grains?
Prabhupäda: Oh yes. But not guru. Ekädasi observed by jiva-tattva, not by Vishnu-tattva. We are fasting for clearing our material disease, but Rädhä-Krishna, Caitanya Mahäprabhu... Caitanya Mahäprabhu also may not be offered grains because He is playing the part of a devotee. Only Rädhä-Krishna, Jagannätha can be offered grains. Otherwise, Guru-Gauränga, no. And the prasädam should not be taken by anyone. It should be kept for next day." (Room Conversation. 22nd April 1972. Japan)
Prabhupäda: They are strictly following Vaishnava principles. They...
Whenever one comes to become my disciple, the first condition is that no
illicit sex; no meat-eating, eggs, fish, nothing of the sort; no intoxication
up to smoking cigarette, drinking tea and coffee; and no gambling. So they
strictly follow these things. In our society, there is no tea-drinking
even. We donít drink tea. So... Intoxication, päna, chäi päna,
päna... Päna is intoxication.
Prabhupäda: Tämbüla. Yatra päpas catur-vidhä.
Guest: (Sanskrit or Hindi: Krshna is offered tämbüla in the temple.)
Prabhupäda: No, Krishna can take.
Guest: Yes. And that prasäda of Bhagavän Shri Krishna...
Guest: ...the devotees can take also...
Prabhupäda: No, prasädam, according to our principle... Just like on Ekädasi day, we do not accept even prasädam. Anna. We keep it. So prasädam... Just like on Ekädasi anna is prohibited, but not the Deity. Deityís offered anna, but we cannot take the prasädam even. So following strictly the principle, even tämbüla is offered to Krishna, it is not for us. Yes. Strictly following the principle. The same example... Just like on Ekädasi day, anna is offered to Krishna, but we donít take.
Guest: The devotees are not allowed.
Prabhupäda: Not allowed, yes.
Guest: Iím very grateful to have your darshana. Om namo näräyanäya.
Prabhupäda: Jaya. Hare Krishna. (end) (Room Conversation. 11th July 1973. London).
HIS DIVINE, EVER REVEALING, EVER LOVING GRACE SRILA PRABHUPAD KI JAYA!!!
Gaura Purnima page