Hi TestDemo,
Yes, You can login with the same account on different devices as well as different platform SDK's. We simply do Login or User Managment like Email account you can login from every where you wants.
If you want to fix it with respect to device, you can choose userName as device ID that is unique and need not to take input from the user for it.
Let me know if more queries are concern.
Thanks
Vishnu Garg