I believe IsGameWon() could be a candidate for the const. Of course it is not like the other Get methods for stating it is not receiving any information it still has the potential to get info for either tell the player he/she is won or lost due to incorrect guesses.
The Reset() I do not think for a candidate for a const. I say this because after the player looses the game starts over from the player command. Reset() values do not have another value or meanings we will not touch .