Right,
Question 2. You should have 2 remote keys and an emergency key which is a plastic strip with the key part on the end. If that makes sense? Usually this was kept in the glovebox but owners would remove them as theives cottoned onto the fact this emergency key was in the glovebox.
I can't say I've ever heard of deregistering a key but I suspect ordering a new one would bit be cheap. If you do want a new one then this needs sourcing from Audi.
Question 3. Audi will have on record all work that has been carried out on your car over the last 10 years and this will include servicing, MOT, warranty and recall work. You should be able to go into any Audi main dealer to get this information. They can also tell you what serve plan the car was on, ie long life or not. You may also be able to ting out to get all this info but I think owners have found it hit and miss as staff aren't always willing to divulge information over the phone due to confidentiality and data protection act etc.
I would like to think that as it's been serviced at an independent garage for the last 2 services then there should be paperwork to back this up?
You are right in saying that there are 2 types of audi service plan and normally the car will stay on the plan it was assigned when new regardless of the miles you cover. Most VAG cars are on long life servicing now. I would like to think that this info is on.the paperwork for the last service and in failing that I'd ring the garage to confirm which servicing schedule it's on.
Question 4. If you are still.on.the orginal battery and the car being 10 years old then I'd say it will be due for replacement soon. The average life expectancy of a battery is 5-7 years. You could always take it to halfords for them to check the battery as they can test it. Also I believe the battery us under the passenger seat, but don't quote me on that.
Hope I've helped :)
Cheers
Steve