No, for the same reason, you have to check if there is no winner yet too.

No, read the instructions again:

0 if it's a cat's game (i.e. a draw).

A game can be solved without filling all the board with X and O.

[[0, 0, 1],
 [0, 2, 1],
 [2, 0, 1]]

I know that example is a little braindead for player 2 but it's a valid example ;)