You can, but it is not a good swap as your speedometer will read 58 mph at a true 60 mph. I don't understand why you would want to go to a narrower tire but if you do you should go to 185/65-15.
Yes, that's a reasonable swap.
It depends on if you have the clearance and the tires don't rub the inside of the fender when turning.>Al
Yes, that is a pretty good substitute.
You can substitute these tries if need be. But if you do this your car will be off balance.
no
Yes, you can substitute the 205/75-15 for the 215/70-15.
Yes, you can
Yes, they can
Yes, they can
Yes you can
No, that is a very bad substitute. If you want to go with a 70 series tire go with a 195/70-15 which is a great substitute.
The rim size must match the tires unless you also change the rims to match the tires.