does this comply with city code? I live in Milpitas, Ca.

The code compliance can only be guaranteed by the person who will review the drawings. We have had cases where one person classifieds a cabin as recreational structure and the other one as a residential structure. We'd be glad to email the drawings so that you can present them to the local building department.

Can it be assembled as one large space with no interior wall?

Interior wall comes with the kit but it can be left unassembled.

Is electricity something you’ve seen other owners add easily into this unit? It looks like their is plumbing pics but no mention of electricity.

The hook-ups are relatively easy for wood walled cabins. Most electricians install the main wiring under the structure near the walls and bring in wiring for the outlets (fro instance) through the floor and simply cover the wires with U shape wire mold. These days many customers simply use LED bulbs with batteries for light structures.