Pairing Apple Watch
If my iPhone is only 7 plus and not IOS 16 does this mean I am unable to use my Apple Watch?
iPhone 7 Plus, iOS 15
No, unless you own a newer Series 8 or Ultra or the newest SE, which is on WatchOS 9. Any watch on WatchOS 9 would require and iPhone running iOS 16 or higher, which an iPhone 7 is incapable of running.