Q: Adding sections to a song - why doesn't the new song play from beat 1?

If you hit the play button, it will play the most recently selected section. You can change that using the song section controls.

See this Help Page: http://help.apple.com/garageband/ipad/2.0/index.html#chs3c3ef5dc

Play a different section

• Open the song section controls, then choose the section you want to play. To play all sections in the song, choose All Sections.Tracks view changes to show the section, and the ruler shows the bar numbers for the section.In Tracks view, you can also switch between adjacent song sections by swiping left or right until the next section is visible.If you set different quantization or transposition values for a track in different sections, the quantization or transposition value for that track appears as Multiple when you choose All Sections.
• Tap anywhere in Tracks view to close the song section controls.
• To play the current section or sections, tap the Play button in the control bar.