The system requirements are written on the Stage Traxx website. You need at least iOS13 to run the current version. Your iPad 3 has only iOS9 and will not be able to run Stage Traxx.
The oldest iPad that will run Stage Traxx is an iPad Air 2.
Purchases can not be moved from one AppleID to another AppleID. Well except when both accounts are in a family. Family sharing is enabled so that you can unlock the full version on any device in your family.