That's not how it works on iOS. iCloud and App Store accounts can be switched independently. After the installation you can switch back to your main account, an

That's not how it works on iOS. iCloud and App Store accounts can be switched independently. After the installation you can switch back to your main account, and all your data will still be there. Newly installed app should auto-update as well. I personally have apps from 2-3 different countries' store accounts on my Apple devices.