The size of the adapter ring depends on the size of the filter thread of the lens used. This is noted on the lens and in the lens cap. 

No, you need to thread the holder onto the lens itself. 

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. 

It works with any camera that has a quarter inch thread on the bottom (normal tripod adapter) 

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