How many materials does this package contain?

There are 26 materials, all editable. 20 are holograms and 6 light beams. All are editable, and animatable.

What version of Blender is it compatible with?

the Asset Browser version is compatible with blender from 3.0 and later, as the Asset Browser was introduced with the advent of Blender 3.0. If you mean the package version for Extreme PBR Nexus, it has no problems with Blender compatibility, just make sure you have the latest version of Extreme PBR

Which render engines are they compatible with?

The materials were designed for Cycles and Eevee

Is Extreme PBR included?

No, the Extreme PBR addon is sold separately.