app compatiblity on iphone
<p>i am new to iphone apps development.i want to develop Iphone applicaiton.which version i need to use and that should support run older and new version of Iphone.</p>

<p>which device is best for testing apps like 2g,3g,3gs  </p>

<p>Thanks in advance</p>

<p>Aswan</p>
