With respect to your (B) scenario, I'm skeptical that a government or rebel group would regard offshore oil operations as stable enough in the long term to consider saving those reserves for future generations. In the coming oil-short era, the country could easily lose access to offshore assets.

Onshore oil could more plausibly be kept in reserve. Sure, it could.

In the government's place, I would want to pump as much as possible from the offshore fields, then invest the resulting cash in some modernization project inside the country.