Yes. Go to this site to compare sizes - and pay attention to the diameter: http://www.miata.net/garage/tirecalc.html
Yes.
The 225/55 tires are wider and shorter in sidewall height, so the height would be fine but you'll need to see if the width works without scraping.
The 225/55 tires are wider and shorter in sidewall height, so the height would be fine but you'll need to see if the width works without scraping.
yes
215/70/r15, 215/75/r15, 225/70/r15. I think that some may have also came with 14inch wheels. I have put tires as large as 225/75/r15 or as small as 205/75/r15 on an 84 without any issues.
Yes
Yes, they can as long as both are the same on each axle.
You can substitute these tries if need be. But if you do this your car will be off balance.
Yes, it will.
Yes /- no problem
Absolutely!! I run 265/75/15r with not problems on my 100% stock xj. You should be more than ok.
No. It is very dangerous to attempt to put the wrong tires on a rim.