maemo.org - Talk - installing nitdroid, multiboot, partion etc

Hello!
I have a nokia n900. I'm intrested in installing nitdroid on it.
I read a how to faq about how to do.
http://wiki.maemo.org/Nitdroid_easy_...lling_Nitdroid
I wonder will it be dual boot or only one OS?
I also see that it will format 2 Gb what will happen to the rest? Will it be meemo or just free memory?

I wonder about this
NOTE: It is highly recomended that you flash the modded 8GB 20GB eMMC image. Nitdroid won't recognize/use/install anything if you have low memory in mmcblk0p2.

Shall I do it before or after the installation and what modded GB?

I also wonder if it is possible to format the phone to different partitions if I would like to install other OS in the future.

Do I have to install multibook or is it made automaticly? Do I need to do it before or after?

Do I need to make an backup? I do not have any programs or setting that I need to save. Only some stuff at my SD card.

Is it possibe to have an iphone emulator too?

I'm a beginner at Nokia N900 but I have some basic computer skills. I know what os, partiotn and formatting are even if I donät know it in maemo version.