Fischer defeats future US Armed Forces Chess Champion in 16 moves

This analysis features the chess game between Donato Rivera and Bobby Fischer from the 1962 Varna Olympiad. In 1964, Donato Rivera was a First Lieutenant in the Air Force and won the 5th US Armed Forces Chess Championship. Fischer opts for the Nimzo-Indian Defense where he plays multiple technical moves early that create concessions from Rivera. These technical details paved the way for Fischer’s final tactical sequence in this 16-move encounter.

Donato Rivera vs Bobby Fischer | 1962 Varna Olympiad

Below the video I have highlighted 2 positions
https://youtu.be/8oLpl_5HaD0

Question 1 of 2: Why does the knight move to e2 instead of f3?

Question 2 of 2: How would you reply to 13...Bb7?

Closing words

Thank you in advance for any likes and/or follows you may give. Any questions or comments you may have can be left on YouTube or in the forum below. If you enjoyed the featured video, you may also enjoy the playlist I've created Bobby Fischer's Chess Games. I hope you have, in some way, benefited from this post. Thank you for taking the time to read.
-Jerry