If you want something like your second line (press any button) then do If B>=0 then goto @sample
When you press a button it puts in a code. Up is 1 down is 2 left is 4 and so on.
And make sure in the beginning you put B=BUTTON().
For 3 and 4 instead of INPUT FILES, put LOAD". If you don't want to see the text at the bottom thats varifies that you want to load a project, then put ,0 at the end.