The VG Pocket is a series of handhelds, currently including:
VG Pocket (50 games)
VG-1500: VG Pocket Mini (30 games)
VG-3000: VG Pocket Max (75 games)
These three contained original NES ROMs, hacks, and/or pirates that were renamed (unconfirmed).
VG-4000: VG Pocket Tablet (25 games)
VG-4003: VG Pocket Caplet (50 games)
These newer ones actually featured some licesened games.
There are also two Disney versions:
Princess Pals
Classic Pals

~ Accessories ~
VG-4006: Caplet Starter Kit

~ Game Lists ~
VG Pocket
VG Pocket Mini
VG Pocket Max
VG Pocket Tablet
VG Pocket Caplet
Princess Pals
Classic Pals

~ Debug Mode ~
VG Pocket & VG Pocket Max:
To enter debug mode on this system, hold down Square and Circle and turn on the power. It will give you the version number, say "TESTRAM FAIL" and display two NES-like controllers. In this screen you may also enter another, seemingly pointless, mode by holding the down arrow and pressing Square. In this new mode press Square to cycle through the colours: white, orange, green, blue, and black. To go back to the debug screen hold Square and Circle then press Reset. Press Reset in either mode to return to the main title screen.
I don't have any confirmation on a debug mode in Tablet, Caplet, or Mini.