If the room looks like a kaleidoscope, go to Settings and switch from DirectX to OpenGL (or vice versa).
Yes, as long as you are downloading the directly from IMVU’s servers. Avoid third-party "room crackers" or "viewer mods" that ask for your password; these are almost always phishing attempts. Conclusion imvu historical room viewer install
Toggle (DirectX) if you have a dedicated GPU. If the room looks like a kaleidoscope, go