It is not possible, therefore many IMs including levy and eric rosen make ghost accounts to prepare for a tournament.
How to stop OTB players accessing my online games?

Fed up with people preparing to play me by snooping on my account, how to stop them?
How did OTB players know the identity behind this account?

Fed up with people preparing to play me by snooping on my account, how to stop them?
Make sure you never share you account information with anyone. If no one knows who you are online, they can't use those games to prepare against you.
Though, sounds like that should help you find weaknesses in your repertoire.

Fed up with people preparing to play me by snooping on my account, how to stop them?
Before COVID, local players did not know my Lichess name so I could keep those private. Then we played there when our club went online. Now I bury them with information. 80,000 games between the two sites. Prepare away.

play on lichess on an anonymous account.
One's Chess.com account is an anonymous as you want to make it - if the OP is really interesting in throwing off potential opponents who may know their current account name and bookmarked their game archive, they can rename their account, which will change the URL for those things.
It won't affect their friends list or their club memberships, so if an opponent is part of the same Chess.com club and can tell who Lippy becomes by the comments they've made in that club, renaming isn't going to help. Nor is this thread, really, which will just show Lippy's current username as well. The quoted text blocks will still show Lippy-Lion, though.

The thing that I did was remove my name from my account, only the people that knew my account before could prep against me, even if I played some repertoires I didn't use online.

Hmm, but how can he remove all trackable traces? He can wipe his friends list. change his caption, country origin. Completely change his whole profile. But what about his game history or anything else?
The thing is, the game history isn't just his, it's his opponent's as well, so those are still going to appear there. If you really don't want any trace, you can play unrated games without even signing in or signing up. That seems like overkill to me, though.
How do they figure out your account ?
They have their ways. I saw this movie once...the guy was in the bedroom with a gigantic knife. Whoa!

Why on earth would anyone waste time studying my games to prepare for a tournament? I usually mess up move orders or forget a move in an opening and get a weird novelty that I have to figure out a solution to right at the board. The rest is just boring generic garbage.

Fed up with people preparing to play me by snooping on my account, how to stop them?
You don't really open with a3 as white and answer everything with a6 as black?
And then get upset if everyone knows that?
Fed up with people preparing to play me by snooping on my account, how to stop them?
Do you honestly think anyone is pouring through all your online games so they can prep for you? And even is they were, what possible difference would it make. Do you have some secret openings the world has never seen? Of course not! Suppose your upcoming opponent learns that the play the Caro Kann. What possible difference would that make?

Why on earth would anyone waste time studying my games to prepare for a tournament? I usually mess up move orders or forget a move in an opening and get a weird novelty that I have to figure out a solution to right at the board. The rest is just boring generic garbage.
they don't tend to do it at our level, but I've seen plenty of 2200+ players do it and I've seen 2000s do it to prep for games against 2000s
When I used to be a regular tournament player about 25-30 years ago, I'd walk around during tournaments and see what people I'd likely play played. But it didn't go into the details of opening sublines. It tended to be more bother than it was worth and it may have had an effect on maybe one or two games over years. Now with databases, GMs have access to what their opponents play down to the variation. It's probably still a big waste of time.

Why on earth would anyone waste time studying my games to prepare for a tournament? I usually mess up move orders or forget a move in an opening and get a weird novelty that I have to figure out a solution to right at the board. The rest is just boring generic garbage.
they don't tend to do it at our level, but I've seen plenty of 2200+ players do it and I've seen 2000s do it to prep for games against 2000s
When I used to be a regular tournament player about 25-30 years ago, I'd walk around during tournaments and see what people I'd likely play played. But it didn't go into the details of opening sublines. It tended to be more bother than it was worth and it may have had an effect on maybe one or two games over years. Now with databases, GMs have access to what their opponents play down to the variation. It's probably still a big waste of time.
People still do that. They'll walk around at tournaments and make mental notes of what their peers are playing, remembering for later rounds or just in general.
One time I played 1.Nf3 which is somewhat rare for me (usual is 1.e4). The person looking at my game was surprised enough that this wasn't enough, they came over and stood right next to me and looked at my scoresheet to see exactly how the opening went
Do any of you think your sub-GM opponents know any secret moves that refute your openings? Of course not! Who care if your opponent knows you play the French or the Nimzo-Indian. These are sound openings. There are no "secret" moves that your opponents are going to produce and refute your opening.
If you are not a GM, your games will be decided by mistakes and blunders in the middle game or the end game, not by some super-secret innovation on move 10 of the Catalan!

Do any of you think your sub-GM opponents know any secret moves that refute your openings? Of course not! Who care if your opponent knows you play the French or the Nimzo-Indian. These are sound openings. There are no "secret" moves that your opponents are going to produce and refute your opening.
If you are not a GM, your games will be decided by mistakes and blunders in the middle game or the end game, not by some super-secret innovation on move 10 of the Catalan!
It helps a lot to refresh.
I've seen people with laptops, 5 minutes before the round begins, they open up 10 GM games on chessbase and scroll through the moves super fast... almost feels like cheating heh.
But it can be the difference between forgetting your prep on move 8 and forgetting on move 12.
Fed up with people preparing to play me by snooping on my account, how to stop them?