Question about caliber 12'''SC

Dear PuristS

I have some question about caliber 12'''SC. Please allow me ask those questions at once.

(1) Is this the first center second movement in Patek?
(2) This is patek original, isn't it? I heard a rumor that this movement have some relation with Piguet or JLC.
(3) I saw a post which questioned the reliability of 12'''SC. Aside from shock-absorber & energy loss comapred to 27SC, does 12'''SC have any serious problem?
(4) This question might be the same for 12-120. How much fragile are those non-shock-absorber movements? Is it very unpractical to use 12-120 or 12sc in non water-resistant case daily?

Thanks

Potoga