Installing on Host that already has version 3

I have hosting on the hostinger. I created a subdomain and created a website with Codeigniter 3.
So the scenario is: in the public_html folder I have a static website that is the domain.
in another folder I have the folder structure of codeigniter 3. This folder is accessed by the address of my subdomain.
Now, I need to create another subdomain to create another site (even if it is in Codeigniter 3, but I prefer to start learning Codeigniter 4).
I already created the subdomain.

The next step is to create another folder structure for codeigniter ( 3 or 4 )?