You can but your speedometer will read 64.17 at a true 60 mph. Your power, fuel mileage, ride, handling will also be effected. If you want to go to a 65 series tire then install 195/65-15 which is a much better choice. Your speedometer will read 62.88 at a true 60 mph with the 195 series tire. My advice is to stick with the OEM tire size your car was designed to run. No good reason to change that.
Yes, you can.
20560r15
As long as all 4 match, the height difference between 65 and 70 should not cause a problem on most vehicles.
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. Your 205 tires will be 0.5 cm narrower and 0.085 cm greater overall diameter. This may cause a minor loss of traction, but in a pinch it'll work.
Yes, you can substitute the 205/75-15 for the 215/70-15.
Yes, they can
Yes, they can
Yes you can
Yes, you can