If you only have one very high level Pokemon(starter or other) that's ok until lance. i recommend leveling up ur weaker Pokemon if u get stuck on lance, or have lots of revives for ur starter.
source: experience( my starter is still my only high level Pokemon)
no beat the elite four first
Yes you do
You never go to Hoen.
Yes
They are still in the Pokemon league
go to the kanto region
Yes they do I can tell you from experience.
nothing
yes you can but you have to beat the elite 4 first
When you beat the elite four.
elite 4 or mt silver
Yes. To unlock it, you must first beat the Elite Four.