3), 5)
Memory management is fully equal standard C++ rules. One importnant thing is that Json lib doesn't copy strings to temporary memory:
https://github.com/anakod/Sming/issues/59
So original string reference should be available all time during processing.
Next, you have a small bug in this line:
BssInfo bss = scanResult->elementAt(i);
It doesn't saved as reference (only local on stack copy of object), so memory will be corupted. Please try BssInfo &bss = .... It should solve problem (but only on last version previous version doesn't love String and requrie const char* vars only)
Another great example is last added network configuration example. It should cover many standard configuration cases and also will show how to use Json lib.