Not possible on iOS, for sure. I'm less certain about Android, though I would ask yourself if such a feature is really necessary, and whether the user would appreciate it or not. What is your use case? An actual alarm? Ads?
Thanks for your response.
Yes, I would say that it is almost Alarm. Instead of an Alarm sound, at a specific time a video has to play in the app.
I have done this with the help of GitHub - wnyc/cordova-plugin-wakeuptimer: Cordova plugin for a wakeup alarm clock .
It works fine in android and the app opens at a specific time.
But the phone does not unlock and wake up at the time. The app opens in the background. I can see the app once I unlock the phone manually.