I was studying for my final when I ran into this problem.
For 1a, I think its O(1) for amortized complexity, because it does x mod N which is sparse enough and linear probing incase it fails
However I'm not sure how to state or prove that exactly.
For 1b, it would hash into the same place, so it would linearly probe more each time it inserts, but I'm not sure how to derive a runtime from that either.