Analogue-sequencer

Hi;

I´ve been reading the cool fast guide,I´m having mastered palylist and parts 
yet, I still find them confusing..

I knew that playlist were as a track on the 909,when you chain your patterns to 
do " a song"   But if parts are the same... What is the difference?
I still don´t know what is the purpose of the repeat option on the playlist.If you 
program as on the 909 a track or song (whatever you want to call them) you 
can do it " on the fly" or pressing the pattern as timesyou want to be 
repeteated,so.. Why this feature?

I guess that I lost something from the beggining.. there was some clues on the 
C3PO files,but his proper London accent was very hard to capture for a guy 
with a cheap "Georgia" kind of english as myself,sorry!

On the 909 if you press several patterns in a row,you do a chain, Can you do 
it faster here than doing a playlist?
If not ,how please?  A lot of hours with both manuals are too much for me..

Another question, I have done playlists just with one pattern to transpose 
them quick and hear how do they fit with my drum patterns,but I don´t know 
how to change the selected pattern to just loop another one. Any help 
please?

Thanks and happy new year!