USB booting :: 5 way usb problem



Hi, i made another thread about this subject and was pointed here, which is absolutely what i need.  Two things, one im very new to linux, but very good with computers and more importantly learning.  I want this exact setup but the most important thing is, do the bootable and embedded OS's run as teh same? do changes in the one reflect on the other? or are u simply just having both on the drive, cause i want them to be the same OS reflecting on eachother.  And if someone wouldnt mind could you type up some more detailed instructions on how to do this,  I would forever appreciate it :D otherwise wish me luck
sorry for double post, but could this be done on a ipod?  or would it screw up the firmware or the functionality of the ipod?  Cause id rather just do that onto my existing ipod then having to go spend more money on a flash drive D: (i know it wouldnt be as fast though since its HD instead of solid state)

original here.