As long as you insert the filters upright into the filter holder and they are not thicker than 2 mm, they will fit.  

For the Nikon 7200 you need a filter in the size 67 mm, this also applies to all lenses. 

Yes, I believe you can with any trail cam. There are several videos on YouTube. You need a 4.0x1.7mm plug. I saw one video that explains a direct hard wire. After watching some videos, I decided it was easier and about the same price to buy the Stealth Cam 12v external battery pack with solar panel. I paid $50 at Academy Sports online. Plus the 4.0x1.7mm plug from Amazon. But if you like to make things, there are plenty of videos on making your own solar battery packs. 

hello , we are the seller, you could use an adapter to step the 52 down to a 49 , there is a adater ring kit https://www.amazon.com/dp/B00JL4HGAI, 

There are 6PCS adapter ring included in this flash, here is the size:
52 55 58 62 67 77mm, as long as your lens size is one of them, then could be used,
Here is the way to check your lens size:
Your camera's lens thread size will be marked somewhere on the lens barrel or printed underneath your lens cap. This number is always preceded by a "?" (diameter) symbol. For example: ?52 = 52mm lens thread size.
If your lens size is none of them, please tell us, we may include the size you need but at this case, this item must be shipped from China so that we could pack with this adapter ring you need.