3.1 couldn’t run in real mode. It could run either in standard mode or in enhanced mode. The enhanced mode was 386-only.
3.0 on the other hand could run in real mode so it technically could be used with 8086.
3.0 would crash every 15 minutes on average. 3.1 would crash every 45 minutes on average. 95 would go a day at a time, 98 would go several days, XP was stable a month at a time when there weren't major exploits or bad driver behavior.
...and so on. I may be overstating the impact SLIGHTLY, but 3.0 really was crash prone to the point magazines heavily pushed people to 3.1 when that came out, and 95 was definitely significantly improved over that, and so forth (skipping ME, of course) until XP.
XP, on the other hand, practically never crashed, unless you had bad drivers. Just like Windows NT4 & 2000 before it.