If somebody cursed Krishna after the Kurukshetra war, does that mean God is imperfect or someone is more powerful than Him?
Q: Why did somebody curse Krishna after the Kurukshetra war? Does that mean God is imperfect or there is somebody more powerful than Krishna?
A: Krishna is not obliged to accept curses because He is Supreme, but sometimes he does so to please the person who made them, to accomplish His own purpose, or both.
Q: In ISKCON we do not kill anything. Then why did Krishna chose to kill so many beings on the land of Kurukshetra?
A: Krishna, although in a superior position, drove Arjuna's chariot in the Battle of Kurukshetra because he valued the friendly exchange with Arjuna more than the position of supreme controller. That is His opulence, that he loves devotional exchanges more than exhibitions of supremacy.
Ksatriyas (traditional Vedic kings) can kill aggressors for the protection of society. That is the dharma. ISKCON is primarily a brahmincal (teaching) movement so we are in general nonviolent. This is Lord Chaitanya's example, and Lord Chaitanya has come to demonstrate dharma in this age.
Q: On Ekadasi day, we can’t eat or drink anything i.e. we are fasting. But can we drink achamana water (sipped in small amounts for purification/cleanliness by priests performing deity worship)?
A: Yes, but just the minimum. Chanting the glories of the Lord is more powerful than fasting. To have more time for chanting is the reason for decreasing bodily maintenance activities.