Q: iPhone 4 cant be updated (iOS and apps)

Hello Community

I have an iPhone 4 with an iOS 7.1.2 installed. I am trying to download a new application that i didnt have and i get the message "Impossible to Download. This app require iOS 8 or newer". I plugged it into my pc and through iTunes it is not possible to update the iOS version. So i cant update the iOS and obviously it is not possible to get a new app or even update one app already installed.

What can i do with this? can i do something to get my app that i need?

Thanks in advance!