1: Tier 1 boots are boots of speed. Tier 2 boots are mobi boots, tabis, berzerker, and etc. Her passive hopping ability depends on the boots tier that you currently have so her passive hop distance is maxed once you get tier 2 boots. Getting an enchantment will not further increase the hop.
2: Her hop is very small so the only walls/ledges you can hop over are the extremely skinny ones like the ledge near dragon pit and the skinny ledges that hold mid lane's bushes. Fat walls dont work. I suggest you go into a custom game and trying Q hopping over various walls. Keep in mind that you should be very close to the wall as her hops are not very long so distance and position matters.
3: Jungle kallista is sort of interesting. The only problem i see is she may have issues clearing and surviving the jungle before she can get items and her ganks don't really pose a threat with proper warding. I can't comment on double jungling in the current meta because I haven't seen anyone attempt it yet. Ganking the lane of her bound partner would probably work but again, her partner would have to know how kallista's ult works in order for the gank to go smoothly.
4: In my opinion, ADCs are the most gold dependent role so running double ADC means the other adc not farming loses alot of power due to lack of items. Running kallista support is very tricky because she needs to get several stacks of her E to get decent dmg off.
Again, you're free to play her in any role. Regarding whether she is viable in any other role, I only see her doing well potentially top and mid as COUNTER PICKS to melee champions.
