vim zajímavé věci o prasatech is that also correct?
That is a correct Czech sentence, but it is missing the very.
and what about ... hodne zajimavi for ... many interesting ...
hodně zajímavé věci = very interesting things
okay. If that is also correct why is the sentence in duolingo different. Does it have to do with cultural issues?? or grammar?
No, it is not correct here. Hodně zajímavé věci means very interesting things. Hodně zajímavých věci is a lot of interesting things, many interesting things, the genitive is used with hodně, málo, trochu, number above four and so on.