NO , rim size is incorrect.
Yes, they can. They must be mounted as a pair.
The equivalence is 225 50 R18 so that the diameter may be the same.
Yes they can
Yes. I've done it. Fits well.
Sure, honey, technically you can slap those 225 55 R18 tires on instead of the 215 55 R18 tires. They'll fit on the same 18-inch wheel just fine. Just keep in mind your speedometer might be a tad off and your handling might feel a bit different. But hey, as long as you're not racing against Vin Diesel, you should be good to go.
Can it? Yes. Should you use this size? No. Your speedometer will read 58 at a true 60 mph. Handling, performance, ride, and fuel mileage will be adversely effected. If you want to go to a 55 series tire then install size 215/55-18 which is an excellent substitute.
Doubtful, that is a big change. You can usually go one size up or down with no problem, Not three.Doubtful, that is a big change. You can usually go one size up or down with no problem, Not three.
No, it will be too large a diameter tire. Handling, ride, mileage, & power will suffer. Also your speedometer will be off.
Yes bigger ones are better for rear wheels
Yes.
Driving in the snow on 225/50/R18 is worse than on 195/60/R17, if the same tires are used.. the tire width is what matters in snow!