It's better to buy a cleaning fluid for lens filter. 

The Answer is Yes. You can use a pinch cap over most filters. ALL my lenses have a filter of some sort on them. I use to use a lot of "traditional" lens caps on all my old Nikkor lenses but putting them on and taking them off became a giant PITA, so I got a Pinch Cap as a test. I then converted ALL the lenses to Pinch Caps. Hope this helps. 

Yes and no. Using motion detection it doesn't work through a window. However.... using the timer inside it you can record through a window using it. How? Set the timer to record 4 minutes every 5 minutes for 1-5 hours or whatever time you need it to record for. This is what I do- just make sure you have a SD card with enough memory for the videos- I use a 32 GB SD card, I use it though a window as a security camera for my car....I live in an apartment so I can't hard wire anything and this works great for what it is. 

I don't see why not, remember that the filter goes on the lens, not on the camera. 

This filter will fit any lens with a 49mm filter thread