On 9A Tosfos mentions that those who had milah in the times of Avrhahm did not need to have a new milah at yitzias Mitzraim since the first one was lshem "geirus".
Who were these people who lived at the time of Avraham and continued to live to yitzias Mitzraim. As far as I know, Yakov was the oldest of the yordei Mitzraim (and the only one to live during Avraham's lifetime and he was not (normally) alive at yetzias Mitzraim.
Thank you, Yakov, for sharing with us your excellent questions. I'll try my best to provide you with satisfactory answers.
As for the first question, Tosfos is actually referring not to those who lived during Avraham's times, but who lived since Avraham's times. This is clear from the context of his words. (In fact, the word "b'Ymei" that appears in Tosfos appears to be a typo, it should read "m'Ymei".)