she lost to stockfish but I believe beat the highest free engine (Maximum 3200) so I think 3400 - 3850
What is the mittens' real rating?

Mittens is rated 1 but, he/she is said online to be about 3600-3900.
though stockfish 15 can still beat mittens, he/ she is extremely good.

she lost to stockfish but I believe beat the highest free engine (Maximum 3200)
Very weird sentence. Stockfish is free.
So lame of chessdotcom to come up with cat bots. Just an attempt to increase engagement on the site. It is about money.

she lost to stockfish but I believe beat the highest free engine (Maximum 3200) so I think 3400 - 3850
1. Stockfish is free and open-source
2. She doesn't always beat the chess.com engine. The only game I've paired the two, Mittens actually lost.
According to Nakamura they lowered its strength, which would explain why Nemo beat it. And he said they would increase it again soon.

Correct!
Stockfish is the strongest chess engine on the planet.
And Stockfish is 100% free.
And Stockfish is much stronger then Mittens. And even before Mittens was dumbed down by Chess.com.
I doubt Mittens is meant to be a strong chess engine by any measure.
Mostly, it's just meant to be a fun little cat bot for chess.com members to try to beat.

Also, if the chess team is increasing or lowering the rating, then I'm not sure what the point is of this thread, my best guess is somewhere between 2000 - 3800
i think it's a bit higher because it drew with stockfish 8