How does the new move “Foul Play” work

Bulbapedia's pretty good on this, but I'll try to answer some of your questions here. When you switch blocks they'll stay like that until you switch them again. They 'level' by keeping that block out for 10 days, and some Pokemon only appear when you put certain objects/blocks of certain levels into the Safari Zone.

The Power of an attack directly correlates to how much damage you deal, because its presence in the damage formula is entirely multiplicative. So, an attack with 120 power will do twice as much damage as one that has 60 power. The same goes with your corresponding attack stat: a Pokemon with 100 Attack will do twice as much damage as one with 50 Attack when using the same attack on the same target.

STAB has operated consistently since Gen 1 so this applies to all of the games. It increases the Power of an attack by 50% if it matches one of your types. 60 becomes 90, for instance.

Technician increases the Base Power of an attack by 50% if its Power is 60 or less. So the most you get is boosting an attack at 60 power to 90. This occurs before STAB is calculated, so your Power would be 90 for STAB, boosting it to 135.