Root Lagfix status before flashing new rom..??

[Rash]

questions..??

1. When we make nandroid backup from recovery, will that backup be deleted by selecting wipe cache partition? Or by selecting wipe dalvik cache (will these two functions delete nandroid md5 backup)..

2. If ever I flash new custom rom, lagfix must be disabled (both data lagfix & system).??
That will automatically convert file system back to rfs..
(is the same flash kernels, lagfix disabled)..modem just flash does not matter about lagfix status..??

Thanks..
Oh yeah can we have multiple nandroid backups..??
If we can they are stored in cwm folder, so if ever phone bricked.. I managed to get into recovery mode > select backup/restore > select restore (Yes)...but will recovery allow me to choose which restore version i want to restore..??
(our does it just restore last backup)...

Thanks All