Update apps codeigniter files on server

We have an app that was developed several years ago.

Recently the app stopped working, functions like login and signup for example dont work, doubt any feature works.

We determined the cause is due to incompatibility issues between CodeIgniter versions and server PHP version.

Server is with GoDaddy and we have to use v 8.2+
The current app's CodeIgniter works only with PHP 7.4

CodeIgniter version currently used is v3.1.1
The newer app's CodeIgniter version is v3.1.10

So as a solution we are considering copying newer CodeIgniter files over the old ones.

i.e We have another newly updated app that also uses CodeIgniter backend. This app works. This app's CodeIgniter version is newer. So we could try copying these CodeIgniter core files to the app that is not working. If you think you could make this work drop a bid or message us.

End goal is to make the app work (Android + iOS)