Will this work for inside angles, crown molding?

inside or out side corners , if your walls are plaster or even drywall the corners may not be a 90

YES. It just measures an included angle relative to itself. The operator must understand the fundamentals of applied geometry and trig to set the miter. ie a 90 degree on this will result to a 45 degree miter. A 137.5 degree outside angle will yield an included 222.5 included back side angle which will yield a 21.25 degree miter setting. Remember to gut your crown upside down. wall leg up and angled out from the fence just like it is sitting on the wall. Inside angle the wall leg is longer, out side angle the ceiling leg is longer. I do not cope my inside joints as some do. I find it easier to miter and caulk as I install. for the price point it is a great tool I even use to to teach applied machine shop math at school and to set my metal lathe tool post angles.

Yes it will. It works exactly like a regular bevel square, only it also has a digital/LCD display too.