I am sorry for the repeat question but I cant find a clear answer. Most of the time PoS isnt explained in detail (only explaining the advantage) and a lot of sources contradict each other and now I am confused.

I think I get PoW but I dont get PoS:

1) there seems to be two types of PoS. One where everyone bets on the most likely block to be picked and another where one node is chosen to validates the block based on the amount of coins you hold and some other factors... is that right? In the first case who decides which block to pick?

2) In both cases it was mentioned, that there was no need for miners. So if you only bet or validate, who creates the block in the first place or is creating the hashes? Or does PoS not use hashes anymore? If yes how do they validate with the ledges of the other nodes?

3) If PoS uses hashes and taken there is no competition of who completes the hash first, isnt there a risk that the chosen one cant compute the hash in time because of e.g. insufficient ressources?

4) Isnt the security less then PoW? As far as I see it, if the function only chooses one node isnt it in theory possible to alter the blockchain? Hashes arent bond by mining power anymore and the current node is the sole active one...