Can i play games frm memory card with updated psp 5.51 firmware

it should be possible if you get custom firmware or downgrade
how you can do this is by using a pandora battery and a magic memory stick
you can buy a pandora battery off ebay or whatever for cheap these days and you can use your current memory card as a magic memory stick
all it does is start the psp in a mode where you can reinstall the firmware with whatever firmware you want.
you will have to research into it because i have done it on my psp
im running 5.00 m33-2
but my psp is a 1002 model

good luck mate,
if you have any questions, email me
deano_90@hotmail.com