Update iOS 15.0

iPhone 6 cannot update further than iOS 12.5.7 due to hardware limitations, this iPhone is too old to run any newer iOS version. If you're in need to run a newer iOS version, you will need to buy a newer iPhone

You cannot do this if you have an iPhone 6......since the iPhone 6 can only be updated as far as iOS 12.5.7.

You need a newer phone.

If you need to run iOS 15, you will need an iPhone 7 or higher model.

If you need to run iOS 16, you will need an iPhone 8 or higher model.

An iPhone 6 is only capable of running “up to” iOS 12.

Newer iOSs require newer iPhones.

The YouTube app requires min ios14. Does the safari or another browser able to use YouTube.com?

You can’t. You need a newer phone.

The Youtube app available on the app Store does not support your older phone.

Yes