1. It is possible, but very unlikely. 2. It was Parangosky, and no. 3. Unknown. If there were, they'd probably be on Installation 07. 4. The Forerunners who survived the firing of the Halo Array believe that their time as caretakers is done. They believe humanity should hold the Mantle.

1. It's possible but not very likely. Of course with the Kilo Five trilogy the possibility of many more Spartan II's once thought dead during augmentations actually survived and were hidden and put into use by ONI exists, there could be a considerable number of Spartan II's out there we don't know about. Even then, highly doubt he would be. 2.Osman became head of ONI after the war with the Covenant. Parangosky hated Halsey for the use of flash clones (although there are contradictions in that because Halsey did not pull the resources nor people for that little op out of her ass and it most likely had to go through Parangosky, same as the whole SII Program). As far as I can tell she doesn't hate the Spartan II's at all. 3. Impossible to know. If there have been other containment failures on other installations then it is possible. 4. The majority,if not all, of the remaining Forerunners side with the IsoDidact, or at least did at the end of the Silentium when they abandoned the galaxy. All known Forerunners who supported the UrDidact were converted into Promethean Knights to combat the Flood, although it is possible he could still have followers that survived the war and went into hiding/cryptums. This involves too much speculation until we know more with future lore.