I've made a few changes to the game play.
1) I added a global for the TimerPeriod multiplier. I've set it to 2 for the moment, to give time to debug. Set it to 0.5 to match what you had before.
2) Two new instance variables on Letter_Holders: AnswerLetter and Done. AnswerLetter is set the the expected letter in that position. Done is when that position has been filled.
3) Hint button added. When pressed, it picks the visible Letter_Holders, then the ones where Done=0, then picks a random one of those. Configures the necessary values, then picks the the appropriate Keys that match the selected letter and hides that Keys.
4) BuildPlayerAnswer function is called when any letter is placed, and rebuilds the Player_Answer based on the consecutive Letter_Holder 'Done' flags.
There's still some cleanup, but this gets you most of the way there.