External Hard Drive with Grub, Ubuntu and Live Ubuntu

Hey folks,

I have an exteal hard drive, wanted to create something like a "ubuntu live usb"-partition. I found some solutions in the web, but i actually want to access "ubuntu live" via a grub entry, since i also want to install a working ubuntu version on that hard disk (and to be ambitious, i wanted to install also a win 7 recovery option, but this is not that important).

I have a partition table with MBR and the following partitions:

sdb1 420 GB NTFS, primary
sdb2 5 GB Ext4, primary boot
sdb3 25 GB NTFS, primary
sdb4 50 GB Ext4, primary

I tried to do it with the "Startup Disk Creator", but he does not recognize the partitions (and i put the "boot"-flag to sdb2 with GParted).

So my first question is, is there a way to put a live ubuntu on sdb2, a recovery windows on sdb3 and a ruing ubuntu on sdb4?

I did not find any answers to that, so I thought about the option of placing an ubuntu iso file in a ubuntu version on sdb4, and creating a grub entry pointing to that iso.
So I installed ubuntu 14.04. amd64 on sdb4 and installed also grub.

I followed instructions of this link:

http://www.howtogeek.com/196933/how-...ur-hard-drive/

in particular i added the following lines

menuentry “Ubuntu 14.04 ISO” {
set isofile=”/home/name/Downloads/ubuntu-14.04.1-desktop-amd64.iso”
loopback loop (hd1,4)$isofile
linux (loop)/casper/vmlinuz.efi boot=casper iso-scan/filename=${isofile} quiet splash
initrd (loop)/casper/initrd.lz
}

/init:line 7: can't open /dev/sr0: No medium found

this line comes around 100 times. After 2 minutes he gives me some information about my hardware, and then he says

(initramfs) Unable to find a medium containing a live file system.

So

• "Unable to find a medium containing a live file system", does this mean, the grub entry did not point correctly to the iso?
• Or does it mean, that my computer did not manage to scan the exteal hard drive in a certain amount of time? I found some similar cases in the web, and some people wrote, that with more power (usb3.0) the problem did not appear. But this computer does not have a usb 3.0 port, and i would like to solve that independently of that.
  
  • Does the fact, that the iso file is placed in the end of my hard disk, influence my computer to find it? I didnt want to place the ubuntu system in the begiing, since i wanted to put there a ntfs partition for data, which is readable windows (i read that there are some problems, and windows does only recognize the first partition)
  • I read something about a boot partition, is this maybe going to solve this problem?

I know I could solve this situation by two usb sticks and a live cd. But i am curious about this, and i only have one usb stick, and i think this should be possible.