Q1. Nothing special happens. All fine.
Q2. Totally true, as far as I know.
Q3. That's most likely a setting, not something in the OS itself.
I run win7 pro 64 bit. It has two "Program Files" folders --- 1 for 32 bit apps & another for 64.
Q1- what happens if I accidentally install a 64 bit app into the 32 bit Program Files folder? And what happens if I put a 32 bit into the 64, bit Program Files folder? Q2- I have read that 32 bit apps will run just fine on a 64 bit OS. Totally true? Mostly true? Or sometimes true? Q3- Why are print & icons so much smaller when running a 64 bit OS versus a 32 bit OS?
(sigh) life was so much simpler when my Apple 2e was state of the art.