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There is no such a feature. I don't remember any app in my phone which have this. Facebook, Telegram, Whatsapp, any email client, browsers, etc... they all don't have any special menu to exit the app. All these apps are stays in memory.

How do you usually exit apps and why? Android is managing and unloading old apps from memory by itself usually.

Yeh you are right in saying that m, but consider whatsapp if we click on back key it gets exited and while trying in this app it doesn't work while clicking multiple times.

Oh, do you mean Android back button/softkey don't move app to the background when you are for example on Feed page wanting to get back to Home screen? Yes, you're right, this is a bug which should be fixed then. Thank you for your report!

So where should i have to report about it.

No need, I've already created a github issue for this.

Ok.
I have an another issue with this app.
I am not able to claim my rewards.
Can you check it again.

This is just not implemented yet. Thank you for your patience! :)