1) This is the trend, PNP usually takes longer than FSW, but there were also cases processed in 3 months. So I guess it is a case-to-case basis too and also depends on the local VO processing your file.
2) I got my nomination in 23 days. That was before OINP closed the registration.
3) I got the certificate 2 days after nomination, I live in SG
4) No, it is not mandatory but you will surely get an ADR for it and the Schedule 4, so better upload these documents upfront if you are a PNP candidate.
Don’t be deterred by the long processing time.
Good luck