Both mine understood the names of quite a few everyday (to them) objects and basic requests like 'can I have/where's the ball please?' at that age, but there is a huge range to 'normal' and as PP I have no idea how common it is. If you are worried it might be worth a chat with your HV even if it is just to put your mind at rest.
No, ds had a hospital check up at 17 months (because he was ex prem) and I remember being worried as he just didn't respond to "where's the....." Questions at all. By the next appointment at 22 months he'd suddenly blossomed, responded to everything and had 80 words. So I think they can just go through sudden developmental leaps.
I’m struggling to remember at 13 months but pretty sure he’s only have looked around if it was something very precious - dummy, bottle etc. Now at 21 months you can ask him for pretty much anything. Much to my shame if you ask for the remote he’ll run and bring it over!