I have created an application and I have purchased an account in AppStore.
I wish to configure the app such that it will run for free twice and after that the user will have to purchase the full version. I want to implement the purchase of the full version inside the trial version (using in-app purchases).
Apple does not allow trial software in the App Store. You can have 'lite' versions of your applications, but Apple requires that they are fully functional applications that do not expire and are not simply advertisements for your for-pay app.
Once you figure out what type of features you want to offer in a 'lite' version, one thing you could do to offer an in-place upgrade for customers in to use the in-app purchase mechanism. Apple now allows free applications to sell in-app purchases. So you could have an app call 'Foo' and inside 'Foo' you could have a menu option to unlock additional features, which would bring them to the in-app purchases dialogs where they could pay you to unlock more content of the app.
Check out Apple's tips & tricks for App Store submission: http://developer.apple.com/iphone/news/appstoretips/
There (listed on Sept. 18th, 2009) you will find a tip titled Just Right "Lite" that reads:
Using a "Lite" version to show how it feels to use what you make and what kinds of things your app can do is definitely a good way to find customers who will pay for the full version of your application. But store shoppers tell us it only works if you follow a few simple rules:
- Make sure the functionality you decide to include is complete. Battles that require weapons only available in the full version, for instance, are annoying and irritating instead of enticing.
- Don't set time limits on your "Lite" version, either for run times or life times. Applications that will only run for a set number of minutes per session, or that expire altogether after some period of time, don't recruit customers so much as leave a bad taste in their mouths.
- Only display the UI for what your "Lite" version will do. Grayed out menu commands, "more track/car choices" you can see but not select, etc. makes your "Lite" version feel more like a commercial than a product, and an annoying and ineffective one at that.
- Do include information about your full application, including an option to buy, in either your application's About section or on the splash screen. Just make sure the option to continue using the "Lite" version is there as well. A good impression lasts forever.
It's important to follow these simple rules not only to create a better user experience, but also because your app will be returned to you by the App Review Team for modification if it is found to have time limits, incomplete functionality, or disabled functionality.
The most relevent part of that text for yourself and your proposed App design is the last sentence that contains "... your app will be returned to you by the App Review Team for modification if it is found to have time limits..."
Here's a good walkthrough on adding in-app features to your app.
http://blog.mugunthkumar.com/coding/iphone-tutorial-%E2%80%93-in-app-purchases/