Once per year. He commanded his disciples to "do this in remembrance of me."

There is no mention of how often, but given Jesus allergy to ritual as opposed to genuine acts of worship, it seems reasonable that this would not be a commonplace thing.

Again... interpretation.

We can get context for how the early Christians understood it by looking to additional sources from that period, e.g. the Didache and the early Church Fathers.

https://www.ewtn.com/catholicism/library/holy-eucharist-in-t...