I was able to find the answer with the help of the Line 6 support team. Thanks to them.
1- This is a "stereo" cab that was commonly paired with a Spider II amp.
2- This is what they call a straight foward cab, meaning that there's no mono, stereo or impedence options. What you see is what you get.
3- This cab contains four 12 inch 16 ohm 80 watt Celestion speakers.
4- The left side of the cabinet is independant from the right side. It's like having two 2x12 cabs in one box.
5- The two speakers on each side are wired in parallel. That's why each side is 8 ohms (two 16 ohms speakers in parallel equal 8 ohms).
6- Yes it can be paired with a Vetta II head and there are many ways to do it:
a) You can use one side of the cab only (mono mode) by plugging one side of the amp (left or right) into one side of the cab (set the 4/8/16 OHM switch to 8 ohms).
b) You can use both sides of the cab (stereo mode) by plugging both sides of the amp (left and right) into both sides of the cab (set the 4/8/16 OHM switch to 8 ohms).
c) You can use both sides of the cab (mono mode) by plugging one side of the amp (left or right) into both sides of the cab (set the 4/8/16 OHM switch to 4 ohms).
This last option is a little bit tricky. You need to know that each side of the Vetta II head contains two speaker outputs wired in parallel. So if you plug these two outputs in the cab (one in the left side and the other in the right side of the cab), the two sides of the cab (all four speakers) are now joined together in parallel. Since each side of the cab is 8 ohms, it becomes a 4 ohm mono cabinet (two 8 ohms in parallel equal 4 ohms). That's why you have to set the 4/8/16 OHM switch of the Vetta II head to 4 ohms. For more information check the Vetta II Manual (Pilot's Handbook) at page 4-47, 4-49 and 4-52.
Vetta II Manual : https://l6c-acdn2.line6.net/data/6/0a060b316ac34f059369d89a9/application/pdf/Vetta II Users Manual.pdf
