The only thing that can happen to you is that you have a powerful adversary that has taken control of all the nodes you are connected to and is trying to run a Sybil attack partitioning the network and giving you only blocks from an alternative version

But for that to happen, that adversary would need to have mining capabilities to produce new blocks of that alternative chain which at the beginning most likely would be very difficult and it will only create blocks very slowly which is very easy to notice

For weeks until your difficulty adjustment of the alternative version works, you would notice and finally even if it’s adjusted .. you would have seen a massive drop in proof of work in the network