Yes.
Should be road legal, mine is ..
Dunno, depends on what else is fitted and how you use it.
I have +5" shocks with +2" mounts and +2" HD springs at the rear, with Adrenalne trailing arms, which give immense droop so had to add in relocation cones to stop springs falling out, and I mounted the springs to the bodywork end and the cones on the axle which worked best for me. I would doubt I'd have been happy with +5" shocks if I'd stuck with stock arms etc. I originally had +3" springs that were too stiff and simply didn't work, so dropped down to +2's which now work brilliantly.
At the front I stayed with only +2" shocks and springs which also work well together with standard turrets. The +3" springs I had didn't work at all, so again, they were swapped back to the +2's. I stayed with +2's 'cos I can't afford wide angle props or castor corrected radius arms or the more exotic suspension fittings to compensate for larger lifts, so it's a compromise between lifting and reliability.
The longer you make the suspension the more you need 'stuff' to allow the suspension to work well without breaking other stuff, there isn't a simple 'buy this, fit that' answer.