Turbo elbow studs

Just a stupid thing, but interresting.
I wanted today changing my factory tuby to a "drop-in" (LOL) 2871R.
Previously I bought exhaust manifold, turbo lines, gaskets ect, and as the Nissa4u and Nissan fast shows, 2 pcs turbo elbow studs.
But, during the swap I noticed, that the original turbo is used with 5 pcs stud without bolts.

Is there any reason using 5 studs, against the factory 2 studs 3 bolts version?

Just another question about the turbo changing.

Whit which tool can I loosen and thigten this elbow nut?

An open ended spanner i would imagine the trouble being the distance between the turbo and block ..... i would guess its easier to pull the manifold with turbo attached and undo it while its out ....