Beat all 15 other gyms, Fight your rival in Mt. Moon and Talk to Blue/Green on Cinnabar island.
The last Kanto gym is in Varidian City.
Blackthorn if you are including Kanto its Viridian Pokegamer01
Blue, the last gym leader in kanto region
There is no 'last city' because you can find any of the Kanto Region cities in practically any order.
It is to the east of Johto, west of Kanto
you have to beat jotho then kanto
In kanto
No, only jhoto and kanto
Latios
yes you can
Maybe in kanto
kanto ,joto