Yes, it will fit any Sony e mount body, either full frame (a7..., a9...), or aps-c (like a6500, etc) 

yes, the flash can work on Canon 7D 

As far as I know it will, I was not informed that Sony had changed the size of the lens mount on the new sony’s A7 models , that would be counter productive to any person owning a Sony lens! 

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 should work just fine. I use it on the a6300 which is the exact same mount as the a7r.