Most important: always check your intended move is no blunder before you play it.
Improvement

Most important: always check your intended move is no blunder before you play it.
Is it true that you only need to be able to see two moves ahead in order to play well?
Or are the best players (IM, GM, et al) able to see many moves ahead (10, 12, or more)?

Here you go:
https://www.chess.com/blog/nklristic/the-beginners-tale-first-steps-to-chess-improvement
Best of luck.

Improving Your Chess - Resources for Beginners and Beyond...
https://www.chess.com/blog/RussBell/improving-your-chess-resources-for-beginners-and-beyond

It doesn’t work how much effort you put because there are too many people using engine assistance . Makes all your efforts go to waste and incentives more engine assistance because if you don’t use assistance you are at a disadvantage and you simply can’t win so more players activate the assistance so the server pushes you to use engine assistance during your games even if you practice a lot do tactics everyday read books and all you get 5 people moving pieces at above ninety even 100 accuracy makes it impossible to enjoy the server or learn or do anything really
Most important: always check your intended move is no blunder before you play it.
Is it true that you only need to be able to see two moves ahead in order to play well?
Or are the best players (IM, GM, et al) able to see many moves ahead (10, 12, or more)?
Depends on the position. If there are many different options, you don't have the time to go very deep. This is usually in the middlegame. When there are few choices, you go deeper. Forcing tactics or a king and pawns endgane are examples where you have to go much deeper than 2 moves.
What are some game changing tips that helped you get out of the beginner level?
It's all about tactics. You can get out on tactics alone. For that you should know about forcing moves and tactical targets: check, checkmate threats and pieces (undefended, insufficiently defended and of higher value).

Learn about type 1 and type 2 undefended pieces, and what constitutes a defended piece. Ideally you want all your pieces to be properly defended until they are ready to jump forward/capture something. Castle early and develop your pieces before making flank pawn pushes or random piece moves for pieces you've already developed. Study tactical motifs.
What are some game changing tips that helped you get out of the beginner level?