How do you identify the liquidity pool of an exchange?

As the title says.

When withdrawing crypto from a CeX, the funds go from a common pool. Let's say I have the wallet address from which it was sent. How do I know whether this is a pool wallet or an individual's wallet?

Another question is, I've noticed that some exchanges periodically sweep funds from several other wallets into one. How does this work?

Finally, can multiple exchanges share a common liquidity pool?

I know that using a CeX is not advisable. I was going through some older transactions though and was curious about the source wallets.