Flashlight on my iphone

Can’t be done.

You can access the Control Centre from your Home screen, and set it to be accessible from within Apps and (separately) on the Lock screen, which should cover all requirements. ( :))

Another option in >Settings>Accessibility>Magnifier would let you access the Flashlight in the Camera App (after booting the App).

On my current version of iOS 14.6, the Magnifier works even with that setting in the “Off” position.

Good luck with it.