iPhone 6 can’t how show update software IOS14.1 my iPhone

The iPhone 6 can not be updated beyond iOS 12.4.8.

You keep posting the same screenshot, but we have already posted the answer. Your phone can not be updated further.

hardware is too old/not compatible.. not enough RAM

Your bank, it looks like, requires iOS 13 to do whatever you're trying to do. this is not a problem Apple can solve for you.

if you have an iPhone 6s.. then you can update your iPhone just like the prompt tells you to do..

Update your iPhone, iPad, or iPod touch - Apple Support

you will need a different phone if you want iOS 14.

A 6s/6s Plus or newer will run it.