Just because older Shin has Sharingans all over his body doesn't mean he can see out of them... Danzo couldn't see out of the ones on his arm, they are not linked like the Rinnegan so it makes sense that he couldn't see Sakura.... I don't think they can control weapons, he marked it with his seal and was able to teleport it similar to how the Fourth was able to teleport to his markings
My prediction: They stated that the Sharingan can teach itself techniques outside of time (How Sasuke learned susanoo and amaterasu from itachi), and that if humans dont evolve they become extinct...... I think each sharingan learned each technique through time, one seen obito's ability and that why they have the space time jutsu, and one eye seen the forth's teleportation markings technique and that's how they are able to mark and teleport objects.... Maybe the eyes got linked somehow through the Infinite Tsukuyomi and gave rise to the altered white Zetsu's (Shin).... but this is just a theory.