After purchase, you get a Steam account with Geometry Dash (No VAC) (DLC may be available). The data is given from the Steam account + data from the mail that is attached to it. All accounts are not linked to the phone. You can link your mail + your phone. You are allowed to change your account information and settings.
For a positive feedback after purchase, you are guaranteed to receive a gift:
Steam account with a random game is completely free. To do this, leave a good review with the mess
Steam