A Microsoft file hosting and synchronization service.
Hello ArunKrishnamurthy,
Welcome to the Microsoft Community. Please ignore my last reply as I misunderstood your question earlier.
It looks like you need help with selecting different photo folders for backup on iOS. That's really the difference that exists in OneDrive between platforms and systems.
The Pixel phones use Android. In contrast, the iPad's iOS is relatively isolated. Most likely it has to do with Apple's system permissions and licensing restrictions. Apple has strict controls over security and privacy protection on iOS, which means that third-party apps are more restricted in accessing and managing system files.
As a result, at the moment, OneDrive doesn't have the same flexibility to back up photos from different apps on iOS as it does on Android.
If you want to backup photos from specific apps on iOS, I'm afraid you'll have to consider manually uploading those photos to OneDrive.
I hope this is useful and please feel free to ask any questions.
Best regards,
Ian - MSFT | Microsoft Community Support Specialist