''Correct me if I am wrong. Have you ever seen the engine proposes a "Brilliant" move as "Brilliant" or as "Best"? I believe NEVER.''
I haven't either
Brilliant Moves in New Game Analysis Report

''Correct me if I am wrong. Have you ever seen the engine proposes a "Brilliant" move as "Brilliant" or as "Best"? I believe NEVER.''
I haven't either
I've seen it plenty of times, it will comment it something like "There was a hard to find move available there".

Brilliant moves are moves that have a sneaky/hard to find follow up but that have nice logic. ALTHOUGH THEY ARE NOT NECESSARLY THE BEST MOVES.
Incorrect.
They have to be the best move.
I swear I saw a brilliant move that was second choice of Stockfish
Possible. That's what happened to me before. I played a "brilliant" move, but the engine has an even better "best" move.

Possible. That's what happened to me before. I played a "brilliant" move, but the engine has an even better "best" move.
Maybe the "best" move is an alternative. The "brilliant" move is a piece sacrifice with a crazy idea that can only be preformed with said move (such as my rook sacrifice)

A sacrifice is a brilliant move
No, even if a sacrifice is the best move, it is not going to show a brilliancy for it. I litterly sacrificed my bishop 5 minutes ago and even though it was the best move, chess.com shows that it was best. Although, if it's a draw but a sacrifice gives you a big advantage they will say that it is brilliant. Depends on the advantage and how good the second best move is (forgot to mention that but you might understand what I mean).

Eric Rosen moment. I moved the king. After they took my queen, I gave a double check, and the next move was checkmate.
1. Kf2? Bxd1?? 2. Nf6+! Kd8 3. Re8#!

Before trading queens, I played a very hard-to-find move.
I sacrificed THE ROOK
This was a brilliant move. It was also the best move.
Brilliant moves are moves that have a sneaky/hard to find follow up but that have nice logic. ALTHOUGH THEY ARE NOT NECESSARLY THE BEST MOVES.
Incorrect.
They have to be the best move.
Most of the time they have to be. But not always. I have before that there's a move which is "best" (6+) and my "brilliant" (5+). Also, it does not have to be a critical move.