Answer:
1. There is no difference between the music from 0:03-0:10 and 1:45-1:52
2. The second theme.
3. At 4:06 we hear the recapitulation.
Step-by-step explanation:
1. They are all the opening introduction.
2. If the repeat of the first theme starts at 1:53, and the repeat of the second theme starts at 2:37, Mozart is developing the second theme from 3:37 - 4:00
3. The part of the piece we hear at 4:06 is the recapitulation.