*.JAD = OTA, over the air installation via the browser
OR, download to PC and move to your Media Card and install from Media > Menu > Explore > find the file > click on and install.
*.cod/alx = download to your PC and install via Desktop Manager.
No, You KAN NOT. You need a data plan for instamapper. Main purpose of the app is to share your location with your friends and family. GPS is free and can locate you. But to share your location the app needs to send some data to the server and for that you need the data plan.