Of course you must know you're going to have to change wheels also as you cannot mount a 15" tire on a 16" wheel. So if you're going to buy a new 15" wheels then you need to mount 225/55-15 tires on them to keep everything as close to the factory specs as possible. This will be an excellent swap.
Yes, you can.
Yes
Yes, if you can live with an inaccurate speedometer.
no
Yes, they can
Yes, they can
Yes, you can
Yes, you can
Normally. yes.
NO, the rim sizes are different.
It is ok, but lessens your overall stopping capacity, - WHY would you want to do that .
Yes, this is an excellent substitute.