I assume with this kind of logic you will be making use of save games :
https://www.scirra.com/tutorials/526/ho ... -savegames
Then to set this up I would automatically load the saved game on start. I would make use of 'On load failed' which returns if there is no saved game present.
'On load failed' - 'Mark as new player'.
'On load complete/succesful - Mark as returning player'
A second way of doing it could be to ghost save the same early on and have a global variable or identifier, which changes based on how late they are in the game and whether you now consider them a new or returning player i.e. beyond an intro movie or completed the first level, whatever you want. In this case, you could just load the game automatically on game start and state the following :
If global variable = 0 - Mark as new player
If global variable = 1 - Mark as returning player
Then play the appropriate intro movies.