All computer games are unrated. Therefore, there is no on/off switch for ratings.
Takebacks are covered in the options section.
https://support.chess.com/article/694-how-can-i-play-against-the-chess-com-computer
How can I play against the Chess.com computer?
Playing against the Chess.com computer is a great way to practice a new opening, or see how a player might react to a new strategy.
To play the computer, just click on the 'vs Computer' button at the top of your home screen: 
OR, hover over 'Play' or the play icon on the left menu, then select 'Computer':
From here, you will be able to select from over 100 different computer personalities to play against, all powered by Komodo!
Choose your opponent!
The first personality of each row is unlocked for Basic accounts. All the rest of the personalities will be unlocked with any premium membership.
Adaptive: The adaptive personalities will adjust their strength as the game goes on! If you are doing well, they will get a bit stronger to try to catch up. If you blunder a piece, they will hold back a little for you. The adaptive bots will do their best to make sure the game is close!
The rest of the bots will play with their own personality and quirks and styles, and will play their hardest to win!
Beginner: These 15 bots range in strength from 250 to 850
Intermediate: These 15 bots range in strength from 1000 to 1400
Advanced: These 20 bots range in strength from 1500 to 2100
Master: These 10 bots range in strength from 2200 to 2450
Streamers, Top Players, or Personalities: Play against bots designed to replicate the style of MrBeast, Danny Rensch, Hikaru Nakamura, and m any more! Can you beat one of the greats? Watch for even more seasonal bots added for special occasions!
Engine: If you don't want to play against any of these new personalities, you can still play against the engine you're used to! Simply scroll down to the very bottom of the bots list and click on 'engine' and use the scroll bar to select a strength anywhere from 250 to 3200.
Options
After you've chosen who you want to play, you'll be able to choose some options. Just like the old computer, you can choose what kind of assistance you want to use, or if you want any help at all.
I play as: You can choose to play as white, random, or black!
Mode: Choose Challenge, Friendly, Assisted, or Custom to decide how much help you want to use!
Custom options: If you choose custom, you'll be able to decide what assistance to enable or disable:
Time: Games against the computer are not timed by default, but if you want to, you can add a timer to practice playing against the clock!
Type: Standard or Chess960!
Hold your mouse over the question mark to see what each option does!
Try to beat them all!
Defeat each personality without any help at all, and they will be marked with 3 crowns!
If you use some help, you'll only get 1 or 2 crowns, depending on what kind of assistance.
How many personalities can you get 3 crowns against?
NOTE: Since the computer is unrated, games with these personalities or with the engine will not affect your rating, even if you use no assistance at all.
Try playing the new computer personalities right now!
I've read all the documentation but it seems to be outdated. How do I enable takebacks vs computer. There also is no way to turn off rated play, which is a step required in their documentation.