Hey,
You can definitely leave Canada taking the next flight...but the concerns will be that you need to have your PR card in order for you to return to Canada which is usually taking around 67 days to be mailed out after your landing date...if for some reason you don't get the PR and need to check into a Government office in Canada then it will be a problem but if your friends or family receives the card and send it back to you in India then you are safe....
Yes, all of your accompanying family members who will be with you at the time of your landing has to be there at least 2years to keep their status validated...If they have honored the PR but decided not to accompany you while you are landing than there status will be cancelled...
For the expiry of entry visa question....you will see that the visa stamped in your passport will have an expiry date...mine was given only for 3months and it cannot be extended or appealed...the duration varies from case to case...hope this info will help...Good Luck