Fantasia_00 wrote:1 - Is version 1.7.4 fully compatible with version 1.7.7 (this one is used in the computers in the class I am attending)?
generally: yes it is. But there are a few differences of course.
Fantasia_00 wrote:2 - Can / Should I upgrade to version 1.8.1 or 1.7.7 (or just leave my actual 1.7.4 version as is)?
I would uninstall XAMPP 1.7.4 and install XAMPP 1.7.7 to be as close as possible to your class computers.
XAMPP 1.7.4 was not the most secure and stable release.
Please follow the How to "upgrade"
guide and never istall a newer version over an older one (XAMPP is not upgradeable!
The older versions of XAMPP can be found at sourceforge, for example XAMPP 1.7.7 for Windows