Mass curves space-time.
Mass is a force acting on space-time.
Mass is outside of space-time.
Your first statement is correct, your second is incorrect (if you mean 'force' in the accepted physical sense), and your third is sort of trivial.
How is this a brain teaser ?
exactly what is the objective of reading those three phrases?
My hand curves a balloon.
My hand is a force acting on the balloon.
My hand is outside of the balloon.
Would this subject actually be the biggest brain twister of all time?
All the information is available,its just the interpretation of the facts.
Separate names with a comma.