Which organ develops and is fully functional in the first trimester 1 heart 2 brain 3liver 4lungs

I believe it’s the heart

The person who utilize the progression principle will keep adding the difficulty of the exercise that he's doing, while the person who does not, will only stay stagnant.  the person that utilize progression principle, will get a stronger endurance because now his body is conditioned to do harsher routines.{the answer was already on verified)