No. The newest Lens Sim versions (v3.#.#) uses OSL camera shaders that were introduced in Blender 4.5, currently NVIDIA OptiX GPU's or CPU rendering in Cycles.

You can still download the v2.#.#-LTS version that uses an older setup, works with Blender 4.2(+) and is compatible on all GPU's that can render in Cycles, but it is slower to render. I will maintain it and fix crucial bugs, but it will will no longer receive any new features.

Probably? Lens Sim uses OSL camera shaders and custom parameters to render and control the lenses, so setups that rely on changing specific camera parameters might not work. Focusing parameters are the same as the standard focusing parameters, so addons that edit the focusing parameters will work as normal.

No. The current system only allows for rays to be traced from the camera and out the lens, not inwards.

I've done some promising tests on generating lens flares, but so far it's just a prototype and there is a lot of work left before I can consider including it in a product.

Yes. The python panel is only there to make it easy to use and alter the custom lens parameters, once a lens is created it does not need the addon to work.

Make sure to include all textures used in your lens setup before submitting to a render farm. Also make sure your render farm supports rendering with the OSL camera shaders that were introduced in Blender 4.5.

No. It currently only works in Cycles, Blender 4.5(+).

However, support for Octane will come in the next update.