Application requires iOS 15.1 or later

You forgot to ask a question.

What application? What model iPhone?

If you are seeing that message, and your device cannot be updated to iOS 15, then you are probably using an iPhone 6 or earlier. You will need a newer model iPhone.

Re: “Softwaee version 12.5.8”

If your phone is running that, it is almost certainly an iPhone 5s, 6, or 6 Plus for which iOS 12 is the end of the line.

Re: “please version 15.5.8 do it”

Saying please will not do it. If you have one of the three models I listed, you will need to buy a new iPhone, preferably one compatible with iOS 26 (or 27, when it comes out).

Nope. If you're running iOS 12, you can't update to iOS 15. Your phone is too old. You need a newer phone.