Only the your onramp/offramp would need to know who you are (because of KYC/AML), otherwise you can be as anonymous as you want and it really isn't hard, assuming you don't want to hide from your onramp/offramp.
First one maybe but definitely not the second one.
Have you actually thought of it?
How would the platform know who sent what. They can't. So it's definitely not shared on the deposit side. And I doubt they'd move the money around because of fees so I doubt it's shared on the withdrawal side too.
From my experience, of course it depends on the blockchain used, but they all have static addresses per user
Why unless? Say you have 1 ETH in Wallet A, if you transfer it to your on/offramp (the exchange) and then do Wallet B, the only link between Wallet A and B is only known by the exchange, so you'll remain private (publicly, again assuming you don't want to hide from the exchange).
You can't trust the exchange to not inadvertently leak the information. A substantial leak could include personally identifying information along with account balances and or deposit and withdrawal totals.
Somewhere along to lines, if you want USD, you need to trust someone, it's inescapable. So once you know this, you can act accordingly.
But still, the original argument was that you have to worry about chain analysis because everything is public, but obviously that isn't true, no matter if an exchange may or maybe not inadvertently leak something.
