Root Some questions on switching between Roms?

[francisco1]

So i am on harmonia 2.09 for the optimus v android version 2.3.7.
I am very new to rooting and flashing ROMS so i have a very basic understanding of switching between them. If i want to say tryout a new rom like quattrimus (cm9) for my optmus v what do i need to do?
From what i know i have to backup my current "ROM" and then clear everything like dalvik cache, factory reset etc, all this from the recovery menu. If i do this will it also backup my apps? If i decide i dont like quattrimus and go to restore in the recovery menu will i go back to EXACTLY how my phone was before?

 

[Nate456]

Yes, backing up your rom will backup the apps you have installed and if switch back to the backup it will be the same just before you backed it up.

 

[AndyOpie150]

When you install a new ROM you need to:
wipe data/factory reset
wipe cache partition
wipe dalvik cache (in advanced section)
format boot, cache, data, and system ( in the mounts and storage section)

When restoring a backup you need to all ^ as well.

If you just are installing an update to the currently installed ROM, a kernel, a theme, a bootanimation, or a patch all you need to do is wipe the cache partition and the dalvik cache.

Use AppTyrant to backup all your apps to the SD card. Use Titanium Backup to just backup those apps that you need to save the data (game scores, level, passwords, etc.)
AppTyrant auto backs up all your apps to the sd card. If you get an update to an app and it doesn't work properly, no problem, just go back and install the previous one through AppTyrant.
Titanium Backup hangs on installing some apps so it's not a good idea to count on it to back up all your apps.

When you make a backup in your recovery it is stored on the sd card in a file named "clockworkmod". It will have a date/time stamp. Write down the date/time stamp ,when you need to delete an old backup you will know which one to delete.
You can use ROM Manager to rename the backup (this makes it easier to keep track of your backups), delete the backup and install a backup that was made with a ClockworkMod recovery. Read the sticky "The Truth About Rom Manager" before messing with Rom Manager though. It will explain what you can and can't do with it.

If you need any help with anything, read the contents of the All Things Root Guide sticky. It usually has the answer to most of the normal questions you might have. You might even find out something you didn't even know you could do to the phone.
If still stuck on something, just let us know.