I want to do update 15.6.1 version but not so any update version

Dine1234 wrote:

I want to do update 15.6.1 version but not so any update version

correct you have an outdate iphone that doesn't have the hardware for the new IOS.

YOu will need to purchase a compatible iphone.

your iPhone is outdated. You will have to get a new phone. Or just stick with what you have with current software.