Boxing & unboxing is the process of converting a primitive value into an object oriented wrapper class (boxing), or converting a value from an object oriented wrapper class back to the primitive value (unboxing).
The Old Dalaran will stay in Northrend, so yes, mages are going to have 2 portals to dalaran (one to Northrend and one to the Broken Isles)
The only case in which section S1-3 of the Laws of Dalaran do not apply are in regards to the Forbidden Magics Act. If the Forbidden Magics Act is broken, Dalaran may arrest, detain, charge, try, convict and mete out punishment regardless of jurisdictional boundaries.