Any previous AIR runtime will not update itself to AIR 2 Beta. You need to download and install the AIR 2 runtime manually from Adobe Labs:
I have installed AIR 2 but without uninstalling AIR 1. Should i uninstall AIR 1 before i install AIR 2?
You don't need to uninstall AIR 1 first.
You do need to do one of these things to make Native Process APIs available.
If you are running the app. using ADL,
1. you need to use option "-profile extendedDesktop",
or 2. set the tag <supportedProfiles> to extendedDesktop.
3. When you want to run the app from installation, you need to package the app in Native Installer format.
Then install and run the app.