Heat and a/c work but no defrost and can't shift air to floor only

That's very weird that styrofoam came out of the vents. Id's say something is wrong with a blend air door or motor but there maybe something jammed up in your vents. A hands-on inspection is needed. Use this link to find a good shop near you. https://repairpal.com/repair-shops Alex

You can blame it on mice ! https://youtu.be/8u5beet98tc