"Solve" means determine if the game is a forced win for either side, or a draw, with best play.
Wouldn't the terms "solve" and "best play" be the same thing? It seems like it's unnecessary to say solve means figuring out the game with best play because there is no other way to figure it out. It seems unlikely chess will be solved with ordinary play, good play, or even great play. The moment best play ever happens for an entire game, chess will be solved at that same moment.
If what you say is correct--then chess has already been "solved".
overconfidence but that is not the opposite of confidence.
Correct. What IS the opposite of confidence?
Insecurity.
Correct.