well the cr-5400 is a good product but if not mistaken, so far i still cannot find a class 4 micro sdhc over here. mostly are class 2 only (class 4 far more expensive for each)

yup, make sure the psp is running OFW 5.03 or lower in order for you to run temporary CFW
memory stick not necessary required to be original, fake 1 will work as well but some report that fake mem stick tend to have problems like file corrupted but some are using it fine

there are alternative to memory stick, you can buy an adapter call photofast and use it with micro-sd, or you can use M2 with mspd adapter, both will work well
cost wise photofast is cheaper, speed wise i think photofast is faster provided u get high class of micro-sd