Yes, you can. Those numbers mean the new tires are about 3/4 inch wider across the tread.
Can and should are two different things. Here are the facts. If you switch to 205/65-15 and the OEM size is 195/65-15 your speedometer will read 58.8 at a true 60 mph. The 205 is .51" larger in overall diameter, it is .4 wider, .25" taller, and your engine will turn 16.6 less RPMs per mile, causing a slight loss of power. This is an acceptable swap but a much better swap would be 215/60-15. This would be very close to the 195/65-15 in all aspects and is an excellent swap.
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
You can change the tires without a problem, just see your mechanic and ask them to try this size out and to see if it will rub against anything. When you change the tire size it would be wise to have your alignment checked out also.
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.