Master RE , Back UP RE and Synchronization in Virtual chasis mode

Hi everybody,

1)Let say we have two EX4200 switches as master RE and back up RE in a virtual chasis mode, we make some configuration changes on master and simly commit it ( we do not use commit synchronize option), will the change still be propagated to back up RE? Is there any minimum interval or it happens right away as we make configuration changes to Master RE?

2)  Is it required all CONFIGURATION CHANGES be entered via MASTER RE i.e we can not go to a member switch and try to make configuration changes there ?  

Thanks and have a nice weekend!!