Yes. This page has a table with some prepositions and corresponding cases.

Because "для" means "for (the benefit of)", and "за" usually means "behind" (unless you exchange things, for instance).

I've found that за only means for in cases like Thanks for that, I am responsible for you.

Because that reads as "Here is butter on the rice."

Обед: Nominative and accusative case forms for masculine singular Russian word meaning "lunch" or "middle meal" = "dinner" (but at a time which would be deemed in American English to be a very early, possibly even a late lunch, or as in traditional Sunday dinner, served in early afternoon. Apparently not the evening meal understood by most American English speakers.)

обеда: Genitive singular case form of обед.

обедь: I can't find this word anywhere. Where did you get it? It's not the verb обедать/пообедать.

Bот здесь is "over here," not "here is."

You can add для to the list of words that force the next word to be genitive.