Yes. Meshes and rig are compatible with Blender 3.x.

However there has been a compatibility break between 3.3 and 3.4 within the shader node system - the color mix node has changed. In order to use the asset in pre-3.4 versions, all the undefined (red) shader nodes in the materials need to be replaced by MixRGB nodes, the  respective settings adjusted to match their 3.4+ counterparts.

To save you the trouble, there's a file "materials-3.3.blend" included in the package. Append the materials from that file into raccoon.blend, and assign them to the appropriate material slots.

No.

The asset is designed to be used in offline animation projects, within Blender.

For the purpose the asset has been made, that is not required.

If you need the skin mesh water tight, fill the eye sockets with a triangle fan.