Eugene, anything shorter than 2 3/4" won't cycle properly. They do not make a mini shell adapter for this gun. (only Mossberg)

Eugene, yes Sir. You will need a mini shell adapter for reliable function(if a compatible one can be found for the Escort Slugger) : https://masonmunitions.com/munitions-shop/

Like Paul said you can but you'd likely run into feeding issues. Hope this helps.

Yes if you load them 1 at a time directly into the chamber, but they will not cycle from the magazine tube
Id stick with 2¾, and 3" shells