Car seats have an average lifespan of 6 years. Better quality ones may expire later. Maybe you can contact inglesina directly on 6844 1188 to see if they are able to advise you further. With regards to placement of csrseat. The safest is actually in the middle. Otherwise if placed on left or right, it is more to your convenience...on which side you want to load or take your baby from
Yes, all car seats should have an expiration date. "Most car seats expire after 6 years from the date of manufacture. If you can’t find an explicit expiration date printed anywhere on the seat (shown below), check the owner’s manual. When in doubt, the easiest thing to do is to call the manufacturer and ask them." From http://thecarseatlady.com/used-and-borrowed-car-seats/
As for the position, yes, safest is at the back seat, in the middle. But do check the user manual on whether your car seat can be installed there, as some car seats require a lap-shoulder belt which not all cars have. I don't think there's a difference between right or left. If you are driving with no other adults, left is probably easier to check on baby.