While picking the PR Card, do they ask for ID proof? As due to some reason i can't go to pick the card?
YES! They sure check your ID and make sure you the one on the PR card. You cannot send someone else to pick it up.
Then notify IRCC that you cannot pick it up. If it's your choice to pickup in person, notify them that you now want to reschedule or have it mailed.
If it's an appointment the IRCC requested, (in some cases, they want PR to go there to show that they are actually inside Canada), then you need to reschedule if you are inside Canada and just not available at the time given.
If you are outside and cannot return to pick it up, apply for PRTD.