QAn opponent changes my follower into an amulet with Izudia, Omen of Unkilling's Fanfare ability. During my turn, if only that follower is put into the cemetery from my field, do I give this follower +2/+2 at the start of my end phase?

ANo. Since it has been turned into an amulet, it is no longer considered a follower.

QDuring my turn, if only follower tokens were put into the cemetery from my field, do I give this follower +2/+2 at the start of my end phase?

AYes. Follower tokens are considered followers, and they are removed from play only after being placed in the cemetery.