I've been work in mapping (some routes and new areas), one of the new areas is this:
This area can been accessed across Pallet City.
Where it is possible to found some fossils, if you have luck.
There is to the Saffron Town:
I will not help much about Saffron Town, i leave up to you whether or not to know what happened, just to talk to the townspeople and they will tell the story (at least give some use to random NPCs).
The same will happen with Lavender City, just New Cinnabar Island history is inserted into the main story.
About Bounty-Hunting, the first two missions are acquired in Cerulean City (Easy Difficult), the following five in Lavender (Normal Difficult) and the remaining three in New Cinnabar Island (Hard Difficult), then there are a few more in the category of Legendary Defficult details here but a little while.
So as a way to forcing you to start the missions of Bounty-Hunting in your first trip to Cerulean City. While not start 1st mission you can not continue to Saffron Town.
I think for now I have nothing more to add (if i has not forgotten anything), so stay tuned until the next update.
Well it took me almost 24 hours...