Key position shouldn't matter. When I was replacing my ignition switch I turned it through all the positions without a key in the ignition and set off about every alarm on the car. I was making sure the new switch worked correctly. After I put everything back together the car started fine.
The key has 2 functions. It has a transponder that tells the alarm control unit (ACU) that you have a legitimate key and aren't hot wiring the car. If your key fob doesn't have the transponder pill in it, or the ACU doesn't have the correct transponder number stored then your alarm will go off and the car won't start. The other function is to act as a remote. This won't work initially, as after 5 days the remote function is disabled to save battery. The remote function is restored after the door is unlocked manually or the car is started. It's one of the two and I can't remember exactly which, but it's in the manual. My ACU "lost" the code for the remote. This required replacing the remote ($250 part+labor) because the code is attached to a paper slip when you get a new remote. The dealership went under and the paper slip went with it...lucky me.
Your ECU may or may not have forgotten the fuel map, but it'll learn that fast enough. Expect a little rough idle at first. I had my battery out for 6 months and when I got it going again I had the following issues. The spoiler was sticking. I got the warning light and had to retract the spoiler manually after the first trip on the highway. I also got a secondary air system failure code, and CEL, because one of the solenoid valves was sticking closed. After a few days, and running the spoiler in and out manually a few times, both issues cleared up.
Radio, you're going to need a new radio code to get the factory head unit working again. Try Loren at the Renntech forums. My ode from him didn't work though.
Here's the link for that:
http://www.renntech.org/forums/index.php?/topic/14539-lost-radio-code-post-your-request-here/
There's a sticky post there. I had to get one from a third party site and paid 12 pounds for it, but it worked.
http://www.radio-code.co.uk/porsche-radio-codes.html