digitech jamman details??

["Jenny Daskalaki" <jendask@gmail.com>]

Hi everybody
I have Boss rc 20 xl which cannot satisfy my needs and I am wondering
maybe Jamman has some more features:
1) Can it save a loop while it is playing without having to stop the 
playback?
2)Can it change the tempo without altering the sound at all?
Unfortunately with Boss rc 20 xl when I change the tempo even for
small differences, the sound is being seriously altered.
3)Can it stop playing the previous phrase and keep the last phrase
during overdubbing?