[Q] Do I need a ROM and a Kernel? topic

Sorry to ask such a noob question but I am quite confused...

My Daughter has a MT1-U06 which I am not sure is either the Huawei Mate or Huawei Mate P6? (there seems to be sections for both that contain MT1-U06)

The phone is a UK model on Vodafone UK, I updated the ROM due to being so old and a couple of problems that have existed since owning the phone but although the ROM's I have tried loaded she was constantly getting "process has stopped" errors on almost everything she tried doing... I tried various different roms which has resulted in the phone working but it locks up quite often now, the long and short of it is I am now not sure what ROM/Kernel I have loaded on the phone and am just looking for a combination of the two (if I even need a Kernel?) that I can load and will give her an operational phone.

I thank you in advance for any advice that can be given.... thank you...