Not much mechanical difference between models.. nothing that casual observation won't reveal. Manuals are for sale online .. Haynes has one and at least one website sells Honda parts-desk microfilm. Did you miss the Owner's manual on THIS same page ? It illustrates controls, etc.
Some later bikes did have batteries for improved accessory function but i never heard of one with electric start.
With the pedal-or-engine lever on the rear gearbox set to engine-drive: The pedals spin the rear wheel. The rear wheel then moves the belt. That spins the variator. Just behind the variator is a small starting clutch. At some low RPM that centrifugal starting clutch engages the engine's crankshaft, and pedal power is communicated to the engine.
The decompression valve vents cylinder pressure and allows easier pedaling-starting. As the pedals spin the engine some momentum is built up and, by then releasing the decompression lever, the engine should fire. Personally i never use the decompression function.. a well tuned bike starts easily.. but a child or any weaker person might find the decompression function useful.
I've got a couple spare engines but have so far managed to avoid ever splitting a case. I haven't bought any special tools for removing the flywheel, variator, etc but i do make my own crude tools when needed.. a welder, drill press and lathe, grinders, etc. are handy. It's not too difficult to damage some things by using the wrong tool or technique..
Near as i can tell, both the "Camino" and the "Hobbit" are PA50's. The 30mph PA50"II" Hobbit is distinguished from a 20mph top speed PA50"I" Hobbit (discontinued in 1981?).
That is the only reference to the suffix "II" i've heard of. The Camino did come in a slower (25km/h) version up until at least 1983 and was sent only (?) to the Netherlands. I don't think the single "I" was applied to it's name.
And, afaik, the different letters, DX, VL, Sport, Custom, etc have to do with minor style variations.. spoke or alloy wheels.. short or long seats, etc.
Some places don't allow 2 passengers on a "moped". Perhaps shorter shocks were used on a single passenger bike.. gross weight and overall height would then be different.
I thought i saw a Camino mounted with smaller than 17" wheels but can't be sure.. I have seen somewhat fancier body work on some Caminos than on others.