I will describe my question using an example.
Let's say the network is working on adding block #100 to the blockchain. An attacker recreates block #99 with a combination of transactions that are "legit", meaning that they can be hashed to the same hash that the actual block #99 is using (and there is no double-spend).
Then, he broadcasts the block to the network. How does the network know that this block is fake and rejects it?
I think it has something to do with PoW, but I'm not 100% sure. Can someone explain to me the process of rejection with a detailed explanation?
Thanks in advance for any answers!