So you're trying to install 3 VMs with different versions of Linux to see which one you like best? Only one distribution installs in VB without a hitch.
1. VB provides an artificial interface between the guest system and your hardware, so your experience in VB may differ from the way that OS would actually perform on the hardware.
2. There are significant differences between the distributions you have chosen, so don't assume they all work the same way. They will be basically similar but there will be small differences to trip you up when you get into details. They will also differ in their default appearance but can be made to look the way you want.
I too have difficulty installing pclos in VB. Part of this is that the moment you tell VB you are installing Linux it allocates a very small default memory to it, which is too small for pclos with KDE. Give it at least 512 MB virtual RAM, a little more (700 ish MB) won't hurt. Secondly, I would suggest at the pclos boot screen, press F3 and select safe settings. You can set up the video once it's installed, but running from an ISO it can be a bit fussy.
And, of course, when an operating system is first installed in VB, the guest additions might not be right, so you might have to click the mouse in the VM's window before the mouse will work in the VM and then use the <Ctrl> key to get out again.