Cable clamp requirements
I have a few questions.
1) Does a plastic box require clamping, or just metal boxes? For example I'm using a retrofit "blue" interior 3 gang box the type with pop in "tabs" at wire entry points. Do I have to leave the tabs in place to pinch clamp the romex, or is it acceptable to pull out the tabs and feed romex through the resulting holes?
2) In another location I am using a 6x6x4 PVC box mounted on the exterior of the house, purpose: to transition four circuits from interior (romex) to exterior (THWN). Four new circuits (romex)enter box from int/ext wall (through short piece of 1.5" conduit attached to rear of box). Each romex connects to a set of THWN conductors which exit the box through separate 1/2" PVC conduits at bottom of box. Is any clamping required, or can I just wirenut all connections and let the wires float?
3) One of these circuits is prewire for a yet unbuilt porch. How can I properly terminate this circuit for the time being? Can I just wirenut the live ends in a j-box? If so, is the attic an acceptable place for the j-box? Someone told me all wires MUST connect to a fixture or receptacle, is that true?
I do have a permit and will be getting this inspected, so any code guidance would be appreciated. My building department is not very helpful with questions.