GQ and GU diff compatibility - are these the same??

[dom14]

Hi Guys,
Please have a look at the pictures and tell me if I got this right.
First four pictures are from a GU Y61. The diff centre housing is Identical to my
RB30 GQ H233B diff centre housing. Bolt holes are the same. Flange is different.
My concern is the Diff centre.
Mine clearly shows the clutch friction plates.
The one from GU doesn't. From outside, it looks like an open diff to me.
My questions are,

1)Is this GU diff an LSD(Limited slip diff) or is it an open diff?
2)Did any of the GU or GQ diffs come with non LSD, standard open diffs?
3) GU diff is marked 4.3, but it must be 4.375. Am I right?
4)Is this GU diff compatible with my GQ RB30 H233B 4.375 diff(other than the flange, which can be exchanged)?
5)Why are the diff centre bit is completely different?
6)Is this better, same or inferior to the 4.375 diff centre I have in my GQ RB30(for RB30 point of view)?

Thanks in advance for any help, advice. I know they are few too many annoying questions! :D

P.S. Housing, axles, bolt holes all match. I'm bit concerned about the "massive" difference in the centre.