DD Boost & DataDomain newbie questions....

1: Not quite right. Data Domain with boot need to transfer all the data to the media server that will then transform the data into hash vales and then only send new data block to the data domain itself. If you want to dedupe at the client you need either Netbackup MSDP or Symantec 5020 appliances.

BOOST communicate with the Data Domain about unique data blocks.

Maybe this video will help : http://www.youtube.com/watch?v=A0vKfAcIve4

2: I do not know - I expect data will not be resend

3:The data domain will only relase a data block if it's no longer referenced by other backups. This is what the weekly cleaning does.

Bonus qustion: Go to the data domain GUI under Data Management -> DD BOOST -> Staticis

Or ssh to the command line and run command 

ddboost show stats interval 2