How to make a word guessing game in App Inventor 2?

I would like to make a 4-letter word guessing game in App Inventor.

Requirements

• Show two of the letters when the user is guessing.
• The user is able to choose to guess which letter.
• The user is only able to guess 4 times, or the user will lose.
• There are three levels of the game: easy, medium and hard.
• There are at least ten(shall be more) words in each level.

My Questions

Should I use 'List' to list out all the words letter by letter?

How to randomly pick the word thus the letters to show?

How is the 'if-then-else' to be arranged?

Should I make label for each letter of the words?

How is the uses of 'global index' in this app?

Is it right to create 3 lists separately(easy, medium, hard)?

etc...(I'm working on this and I will surely update the problems I've come across, so please help along, thanks a lot!!!)