205 is the width, R15 is the wheel diameter and the 55 or 60 is the profile height therefore the 60's will give a sightly more comfortable ride where as the 55's will ride slightly harder.
20560r15
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, they can
Yes, they can
Yes you 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.
It is an acceptable substitute, but know that your speedometer will read 58.7 at a true 60 mph.