He just decided to pass the responsibility on to an unknown person:
And this is a complete lie, I never shared my personal email on a public XenForo site.
If you use cPanel you can follow this guide:
https://www.inmotionhosting.com/support/website/cpanel-multiphp-ini-editor/
Otherwise, ask your hosting. They should be able to make the changes.
It's expected, because the license is associated to a particular URL and if you are running a dev site on a different URL then the warning comes up. As long as the testing site is password protected then you are fine.
I think your FTP client uploaded the files in ASCII mode instead of Binary (that tweaks line endings and breaks the checksums XF uses to verify file integrity). What app are you using?
Trust AI as you trust a lawyer. You must understand what you are doing. Otherwise you'll find issues and could make a mess regarding SEO and conflicts between both platforms. Move XenForo to a different folder (name it "community", for example) and that will get rid of the issues.