Android,iOS App & DB Hosting

[Ravindra Chigurupati]

Hi All,
We are new startup & new to mobile apps. we have given project for android &iOS app for different company. They are developed android and iOS app with database and Admin panel. They have used PHP, Yii Framework , MySQL DB etc for development. Now i would like to host my applications in Servers/Cloud.

1. Android & Apple Dev accounts are ready , so just i can place my apk & ipa files in there for customer access right ? if i am wrong let me know
2. Where can i host DB and Admin Panel , so can go with Servers like Hosting Raja,Blue Host ,GoDaddy etc or any Cloud service is good ?
i heard about AWS , Google Cloud and MS Azure .. these are ok to host ?
3. Which one is fast and reliable from above cloud or normal web servers.
4. We are doing like Water business online so my vendors and customers will register all the time , so customers will access the data of vendors. We have to get Push notifications fast also for orders.
5. My application developed client says they have own servers to keep the apps with them, but i don't like to put there. Can i put there ?

Please clarify my doubts about this, i am fully confusing.

Thanks,
Ravindra.