GCM wants to do noti only at certain times.

There is no function to reserve time at Gcm corresponding to number 1. It is usually controlled by combining time and push transmission on the server.

(Not recommended) If you want to implement it only on the client, you can use AlarmManager to control it as if it was pushed at a certain time. However, exceptional treatment is required, such as when the cell phone is rebooted. Regarding this, you can get a hint by looking at the following topics.