The 88's used a traditional fork, while the 91-up used the inverted fork, the triple clamp from the 92 will fit the 92-up forks, you can use the inverted forks, but I don't know how much work is required to fit them
Yes, if you're putting the ENTIRE front end off of an 1100 on your '88. The bearings and stem assembly of the triple clams are interchangable.
No, if you're trying to put JUST the triple clamp on using the fork legs from your '88 forks. Why? because the diameter of the '88 fork tubes is MUCH smaller than the diameter of the 1100's Up-Side-Down (USD) fork legs. And no, you cannot put shims in the USD triple clamps to allow for the smaller '88 fork tubes to be held. They'll move when you hit a bump. Trust me on that.