No its not mandatory to produce Class VIII Passed Certificate for joining the Post of Group D. MP Pass certificate will suffice in this regard. As far as I know, the School Service Commission as well as the WBBSE did not seek Class VIII Paeesed Certificate from those who have passed MP in any phase during the selection procedure or issuing Appointment Letter to any Group D candidate.
A candidate may change Institution after passing VIII , in that case how shall PVR be made ? As in PVR sheet it is to be mentioned about attended school.
There will be no problem. According to his sheet he/ she must mention his/ her last attended school and then mention about his/ her previous school from where he/she passed VIII.