I need I phone 6s iOS 10.2.4
i need I phone 6s iOS 11.2.4
iPhone 6s, iOS 15
Both iOS version you are looking for does not exist.
iPhone 6s, iOS 15
Looks like your iPhone is up to date.
If it is an iPhone 6S you can update to iOS 15.7.8 (can’t be update to a higher iOS), see -> iPhone models compatible with iOS 12 -> iOS 16.
iPhone models compatible with iOS 15.5 – Apple Support (UK)
or see: