The aircraft is one of many in the presidential fleet. I am fairly certain the seal is permanent on all of them and not something special for O.
And it won’t be called Air Force One until he’s been inaugurated.
the presidential aircraft are 747’s
757 is for the VP although he used to use a 707 that was the first airforce one under Kennedy
technically any aircraft the pres is on is called airforce one
unless it is the helicopter then it is marine one