I'm not so sure how similar Oscar and Alex's styles were. I thought Oscar was more a swarmer, crude...
Alex Stewart and Bonavena weren't anything alike other than having decent punching power. Foreman was kryptonite for short aggressive guys. Bonavena meets the same fate as Bert Cooper.
Stewart was a taller guy with long arms, and against Foreman he used plenty of lateral side to side movement. Not sure why he made the comparison.
If by "Old Foreman" you mean early 90s version, then the answer is yes. 91 Foreman was stronger, heavier and with a better chin, had better cardio and he was more well versed and skilled. If you mean 96 Foreman, then no.
I'm skeptical about this, as we've previously discussed. I think the main difference was a better defense.