1)
Why did he say both that he is young, and that they are old?
1.
Malbim: These are two reasons why he was quiet until now. (a) He is young. (b) A youth should not give his opinion in front of elders at all. They were very old, so he should have waited many days.
2)
What is "Zachalti"?
1.
Rashi: I feared. Ibn Ezra #1 - "Zochalei Afar" are called so because people fear them. This is like "ha'Emim Lefanim."
2.
Ibn Ezra #2: I sat in back. So is Zachalti in Arabic. "Zochalei Afar" are called so because they go opposite to how people walk.
3.
Malbim: I was like "Zochalei Afar", and afraid to lift my head.
