Android 5.0 (API 21) and above.
The “Premium” version enables such features:
If less than a week has passed after the purchase, then contact Google Play for help and they will automatically refund your money. If it’s more than that, email me at email@example.com and send me your purchase ID that starts with GPA and I’ll try to help you.
When you purchase Tilla Premium, in Google Play, it will be assigned to your Google account. If you use the same Google account on a new or factory reset device, you will have access to all previous purchases.
One of the main reasons, why you don’t receive any reminders from the Tilla is your device. On some Chinese devices (OPPO, Xiaomi, OnePlus, etc.) and some other devices, manufacturers make some kind of “battery/system optimizations”, which may affect how Tilla works. You need to disable these optimizations for Tilla and try again. Check more information about your device - https://dontkillmyapp.com/.