How to develop an application which will be compatible for iPhone and iPod Touch 2.0 and above

I have a requirement of developing an application which will be compatible for iPhone and iPod Touch 2.0 and above. So I have number of questions.

1) Do I need to take care of all the deprecated methods and how?

2) I t开发者_开发技巧hink there is no support for GPS/Camera before 2.2.1 so what is the best way to handle this using version below it ?

3) Will testing the application on simulator for different versions be OK or do I need to test on actual devices of different versions?

4) Can this be developed quickly or it involves lot of coding?

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I can't answer question #1 with certainty, but here are a few answers:

2) If there is no support for something you generally need to hide the feature from users who can't use it. For instance, Apple will reject apps that talk about vibration on devices that don't support it.

3) Testing on the simulator is inadequate. It will not necessarily reveal problems you may see. You need to test on actual devices.

4) Any good iPhone / iPod app requires a fair amount of time to test and design properly.