Quick ref:

For those not in the know, this is 616 canon, not an AU or What If...-

The greatest atomic scientist on Earth, Otto Octavius was a respected but often disliked member of the scientific community. His fantastic mechanical arms allowed him to safely handle dangerous materials, but one fateful day a simple error resulted in those arms being fused to his body. The traumatic experience, either psychologically or due to radiation damage to his brain, caused him to become a megalomaniacal villain out to prove himself the greatest mind on Earth. Adopting the mocking moniker used by his peers, he became Doctor Octopus! One of the most dangerous men alive, he battled many superheroes but in particular his nemesis Spider-Man.

After years of beatings inflicted on him during his criminal career, Doctor Octopus was dying. As his last-ditch revenge, he attempted to swap minds with his arch-enemy and leave Spider-Man dying in prison whilst Otto Octavius obtained his powers, youth and identity.

He actually succeeded. But rather than use his new life for personal gain, through the influence of Peter Parker's memories and a promise to the man dying in his body, he vowed to prove himself a hero- the Superior Spider-Man!

Basically trying to be a hero whilst using villain methods, he's a huge jerk but very efficient. He founded Parker Industries and proved himself a good businessman and inventor, got a girlfriend (the lovely Anna Maria Marconi) and was generally pretty good at having a civilian life. However, his brutal approach to crime fighting left something to be desired.

Eventually, he surrendered Parker's body back to the rightful owner as he realised he was unable to defeat Norman Osborn, the Green Goblin. Sacrificing himself so Peter, the truly superior Spider-Man, could save his beloved Anna Maria.

A digital version of his consciousness from before that point obtained a body that perfectly combined his own DNA and that of Parker's, granting him all the spider powers, youth and fitness but with features more similar to his original body. Sans being a big fat old man. He assisted Hydra in their takeover of the United States and was made the leader of their 'Avengers' but had no loyalty to the organisation or its tenets, merely using it as a way to obtain their resources. Later after that was done, he protected Aunt May from Norman Osborn's latest psychotic episode and after leaping in the way of a deadly attack meant for her, Spider-Man declared that even after all they'd been through he was giving Otto a clean slate- what he did from there was up to him.

Still wishing to prove himself Peter's superior, he used the title of Superior Octopus and took the alias of Elliot Tolliver for his civilian life, working as a professor at Horizon University to be near his beloved Anna Maria Marconi. While almost literally everyone sees through the lie, he pretended not to be the original Doctor Octopus but didn’t deny it when people call him out on it.

After a short while as the protector of San Francisco, Otto needed a change of wardrobe and as part of a spider-people event took up the Superior Spider-Man moniker again. He decided to keep using that title afterwards. Getting better at the whole hero thing step by step.

I play Otto at all canon points and will usually roll with whatever seems most appropriate for a particular thread. When playing Otto in Peter's body, I'd prefer if other characters not see through the ruse without prior discussion.