APP can connect multiple cameras at the same time, it is recommended that one APP connect no more than 40 cameras 

yes you can stack the adapters and do that. 

The od size is 100mm, the set comes with multiple different sizes to fit many different lens. You do not need long exposures for good moon detail, 500 sec at f8 works good on full moon 

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. 

There are 7 filter ring adapters, included 52mm/ 58mm/ 62mm/67mm/ 72mm/ 77mm/ 82mm, so it support a CPL filter.