iPhone iOS 7 restore from backup

[Spectrum]

Hello - I am running an 8GB(!) iPhone 4S with iOS 7.
I continually keep running out of space, despite purging data/photos. iTunes says I have 2.21 GB of storage listed as "Other". I'd like to delete it. This is as much as I have in Photos and Apps put together!

I read that you can effectively delete "other" by first erasing the phone, then restoring from an iTunes backup.

My question is: Will this allow me to reinstall iOS7? Or will I be forced to upgrade to iOS 9?

Thanks!

 

[C DM]

If you simply use the option of erasing contents and settings that is aboalble from iOS on the phone then you will remain on whatever iOS version the phone is already running. If you do a restore via iTunes then you will typically get the latest public version available for the phone installed.

 

[alp00]

I'm not sure what Other is maybe it's iOS , when you go to general -> Usage on your phone what does it say ?