Hacking ps vita not downgrading

[malaken]

so, i have followed a few tutorials and i cant seem to get my vita downgraded. i have followed all steps i have found but for some reason it stays on 3.73. i dont know why it isnt, working tried a few different ways with no success. if it matters i have the slim variant. any help would be great. or any way to go about playing games on 3.73 including psp games