It is still a big question of sorts whether the Marvel Cinematic Universe (MCU) is Earth-616, the same as Marvel Comics' version. Before moving ahead with the details, let's just consider this ...

Marvel Studios thrives on speculations and fan theories, and the recent one for The Fantastic Four: First Steps is another addition to this list.

Before Marvel confirmed RDJ was returning to the MCU to play a different character ... unlike what happened on Earth-616. We have already seen one such reality where the Ultron project works.