How do you unlock the major heists in gta v story mode?

The verified evidence from the Wikipedia article on the development of Grand Theft Auto V discusses the game's release history, development team, and related projects like Red Dead Redemption and Max Payne 3. However, it does not include any details about the game's heist mechanics, prerequisites, or the specific steps required to unlock major heists in story mode. Since the evidence is limited to development and release information, it cannot be used to answer the question about heist unlocking. For accurate information on this topic, users should consult gameplay guides, official manuals, or reputable gaming resources dedicated to GTA V mechanics.