Questions about layers 2’s

I have been in crypto for a while but I just decided to get into some of the Dex’s.

The gas fees are brutal when swapping with normal Ethereum. So I have two questions about layers 2’s

1. How many different are there on Ethereum? I remember hearing about polygon a lot last bull, but someone said not all layer 2’s are coins like polygon which was interesting.

2. Will layer 2s work with anything Ethereum? I got into using Dex’s because I wanted some of the mid and micro cap coins I couldn’t find on exchanges. (I have bought smaller cap coins on exchanges before, I know how risky they are price action wise. It’s only Dex’s and self custody that I’m new to).

Thanks.