It'll probably be mush until the Acetone evaporates.
Most likely. Acetone will also dissolve butyrate which will re-solidify as the Acetone evaporates.

I would be very careful with styrene tho as it's sensitive to a wide variety of petroleum distillates and light hydrocarbons.

I'm in the process of cleaning up from a major flood in which i lost a full tank of heating oil in my basement. Styrofoam peanuts all melted and have re-solidified, they look like disgusting hunks of snot. However, they are quite hard and thier edges can be sharp enough to cut you. Rigid foam insulation also dissolved and re-hardened into dense, hard, and sharp chunks of styrene plastic.

My point here is that some of the distillates and hydrocarbons found in the fuel oil are also prevalent in a number of stains and finishes that we like to use on speaker cabinets. Be careful what you mix, and/or expose.

I don't see myself using that anytime soon ! My luck I would be getting my fingers stuck to everything !
Just to clarify and reiterate, there's no danger until it is heated to the point of combustion or just slightly below. Keep the soldering iron and open flame off it and all should go well.