As you will be able to tell from this Question I’m very new at this. I’m building the Hanger 9 corsair .60. I’ve taken a lot of time with this project and ever thing looks great, that is until I tried to put the canopy on. I first installed the canopy using canopy glue, but the canopy does not fit well at all on the plane, and their was gaps all around after taping ever where. I took the canopy back off and reinstalled using “Zap A- DAP-A GOO” Thinking this would fill the gaps. Ever thing look good UNTIL I started cleaning the glue off with Acetone, WRONG! It worked great on the plane but ruined the Canopy. ATE the Plastic!!!! Help

It is a fact of life that acetone is a solvent for plastic.

Other aggresive solvents to keep away from plastics are toluene, xylene, methyl ethyl ketone (MEK), and nitromethane. CA glue also dissolves some plastics.

Many degreasers will eat/craze plastics too.

Will it hurt Monokote? Just used some to clean some dribbles after doing the CA hinge thing

No

I think MonoKote is a polyester type of material, pretty much resists even the most agressive organic solvents. The generic term "plastic" includes dozens of different polymers each with it's own peculiar properties.
PTFE, high density polyethylene, cured epoxy, polyester are pretty insoluable, even in something as strong as methylene chloride.

PVC, polystyrene, ABS, and acrylic will melt in a strong organic solvent.

But it does get the glue off...

I just keep a little acetone around in case I ever glue my fingers together.

you should be able to order a new canopy from www.horizonhobby.com I always screw my canopys down rather than glue them for many reasons including easy replacement in case they get damaged/scratched some how, lessons learned I would guess.
I am surprised you didn't notice the paint melting off before the plastic started .

Easier way to get glued fingers loose is simple water....... stick your fingers in some cold water and let them soak for a few minutes..... CA hates water...... I learned that in my R/C Boat days... nothing glued with CA stays stuck in the water