Many of the thousand data base setups use technichord. Some of these technichords use a different voice on part 4 so the harmony can sound in 3 different right hand voices. If part 4 was not automatically assigned to easy record you would not hear the same sound on playback of the sequence as you hear when playing live. This is why part 4 must be a default easy record track. If you do not use technichord, and there is no part 4 assigned in the setup you will not hear anything on that track because it will be empty. If you don't want to use technichord, use part 4 for something else!

The second part I answered before in your previous thread, although I fail to see the logic behind the question.
If you want R1 and R2 free, easy record on them, then copy the tracks to free tracks, assign these tracks to other parts, and erase R1 and R2.
Otherwise just record apc and control and multitrack normally afterwards to however many tracks you want, leaving R1/R2 free for live playing on top of the sequence. Since you can't record 2 different tracks simultaneaously in the right hand, I can't see any difference in using R1, R2 or any of the other tracks when multitracking.