1)
Why did Elisha pray only that Hashem open the youth's eyes, but not for the horses and chariots?
1.
Malbim: [Always,] "Choneh Mal'ach Hashem Saviv li'Yre'av" (Tehilim 34:8). A Midrash says that camps of angels surround Ish ha'Elokim. Those sent to save him now took the form of chariots and horses of fire, like Machaneh Aram came. Tefilah was needed for one who is not prepared for Nevu'ah to see a great miracle.
2)
The verse implies that Elisha was on the mountain. He was in the city!
1.
Radak: Hashem showed the youth that they will be around Elisha [to protect him], to strengthen the youth's heart, lest he fear.
