Standard outlet cover screws. Length depends on the depth of the setback.
Please check the dimensions of the switch vs the dims listed on the website "Aifittings.com"
This item is actually 4.188" high.
These only need to be installed when the original electrical box is not flush to the edge of the wall.
This item is not designed for this use.
Yes it does.
Cutting the sides of this item will not meet code. Arlington does manufacture a 4 gang box extender, but it would need to be purchased at a regular electrical distributor.
The maximum depth of this box extender is 1 1/2”. Sounds like you have an extra 1/4” to play with. Remember, the box extender fits inside your existing box.
This item is designed to extend an existing box by 1.5 inches. The 2 inch screws provided allow the box extender to be used only up to this depth.