1. Haven't used the tilt viewer for ages so can't say. Didn't know anyone was using it so I never test it 2. Nothing is 100%. Depends what you're doing. GLTF is pretty good though as it's tested and updated regularly 3. IMM player is open source. We actively maintain a fork of the player and use it to build the web viewer. 4. The live Icosa site is currently based on a branch of the viewer: https://github.com/icosa-foundation/gallery-viewer/tree/tooling/poly-comparison because I haven't got around to cleaning up the branch enough to merge into main - it's been based on the branch for the last couple of weeks. 5. NPM is out of date. I should probably make that clearer in the readme.