can first year students select upper year courses if the course requires no prerequisites?

Yes, but don't. You will be screwing yourself over. Second year courses are much more difficult than first year courses.

yeah...i know....but i wanted to take sanskrit and found out that the only sanskrit available was a 3A06
i do have some background knowledge in sanskrit....i know how to read/write it as it is written in the same script as my native language - hindi. Also since hindi arises from sanskrit.... there ought to be some similarities.
so i was just wondering ... maybe it wouldnt be that difficult.....
dont know though......

Languages tend to be a little different. There are some second year russian and polish classes for example -- but they are introductory the same i assume the sanskrit is.