No, not really. I do tend to keep personal information off social media sites, but I don't go back and delete content. Honestly, I think it's more annoying when people do that, and I'd rather leave discussions and references intact that remove this stuff.
I do delete my teweets every few months. They don't get any engagement, and any that would ever see them already did.
Rarely. I leave my mistakes to cringe at 3 years from now. It's not so bad. I cringe more from reading old code.