Many people said that the pc port didn't have lightgun support and I had a huge argument on youtube comment section about this. But then I decided to check again and got bamboozled to see that there is no light gun option on the pc port. But I remembered very well that there was 2 light gun options on pc version.
And I finally figured out why this option was missing. For some weird reason, the lightgun option won't appear if you start the game on direct 3D mode, which most of us do. Start the game in ddraw mode and voila, the lightgun option is now there in the settings!
Interestingly if you set the input device to lightgun in ddraw mode and then start the game in d3d mode, the lightgun option now becomes permanently available in the 3d mode as well. I guess it was a bug. Nevertheless, the game does have lightgun support.
I don't have any lightgun and my old CRT is in my dad's office, so I can't use it anyway. If anyone here has an old CRT and a pc lightgun, please do let me know how well it works. I can set the input to lightgun but then I can't shoot since I don't have one. Here's a video showing the lightgun option [only 1st minute of the video is relevant]:
Screenshots: