characters ask for what they want back? I assume the application informs them they can ask for anything from their home reality
otherwise that would be kind of unintuitive

yes, the application will guide them through this and tell them if their request is redeemable or not (so they can initially ask for something they never had, be denied, etc). there will be a section in the FAQ regarding the phone and it's applications coming up soon. in the mean time, characters can enjoy being confused over it.