As per current trend, The time difference between AOR and nomination is one and half month. Most People who got AOR in March, 2016 , have received nomination in May Mid.
About your second question, OINP may call candidate for queries mostly related with their past employment (Most of the candidates have been asked about their past employment), Also people have been told to provide latest bank statement (even if one already sent with application ,3-4 months back, they may require fresh ones)