Not sure if I ever did send it to you. For now the e-mail is bounced????

Could it be the reason that PHP7 isn't supported yet?

Opencats has a minimum supported PHP version of PHP 5.5, and are working towards full PHP 7 compatibility.

In mine opinion there is no difference; domain or sub-domain

Make your own logo at 277x52 pixels and saved it as: applicationLogo.jpg

Replace te original logo in .../opencats/images with the one you just made.

Done!

For the footer tekst you have to dig into the code.

Greetings
Manuel

Make your own logo at 277x52 pixels and saved it as: applicationLogo.jpg

Replace te original logo in .../opencats/images with the one you just made.

Done!

Greetings
Manuel

Yes it is possible. But you have to dug into the source as you did already and make the changes on several places.
I've translated Opencats to the Dutch language and used Windows Grep and Notepad++ as tools.

Yes I think so.
I assume you made a backup of al your data.

Remove the file INSTALL_BLOCK and start the installation. It will be on the same directory

Choose to restore your backup

It's true it has to be done in the Database.
Therefore keep a backup with those changes if you need to re-install

No there isn't.