Can we send notification when app is closed?

I was searching on the community on this topic but i didn’t find any satisfying answer for this.
I encountered this extension but it works on when the Target SDK is 22.

Is there any better extension for this which I couldn’t get my eyes on?

you can send notification if app is closed.
use push notifications from experiment catogary.

Thats OneSignal, I have to manually send the notification from their website, that is not what i am asking for. But what I want is, something like alarm.
For example, like there is a task to complete by users which is now available for him and he gets notified for that at a particular time.

you can also set their to automatically send notification after a period of time.

Brother your are not understanding what I am saying…

You cannot with the application as they do not run in background.

But you can schedule pushes with Zapier.

You can see it here.