[TYPO3] sync between different versions of Typo3

[Bing Du]

Hi,

I'm investigating what sync options are already avaiable for use.  Based
on the sync related extensions documents on typo3.org and the threads on
typo3-dev, looks like rsync is a way to get files covered.  Speaking of
the dbsync ext, can it sync the databases between 3.8.1 and 4.0.2?  The
direction is 3.8.1 -> 4.0.2.  I recall when you import 3.8.1 dbdump into
4.0.2, you need to do some compare to make the database version
compatible.  If I decide to use dbsync, does the initial sync needs to do
database compare?  Does it have a command line interface that can be run
in a cronjob?  I'd appreciate if anybody would shed some light on this.

Thanks,

Bing