May I know what is the sensitivity of the accelerometer and the gyroscope in all the generations of iPads and iPhones?

First, this is not the best forum for questions like this. You should probably be at the developers' forum, which you will find on the developers' site:

https://developer.apple.com/devforums/

I suggest you ask in the iOS section. I happen to be a programmer so I can answer, but this is about the limits of my expertise and you'll find better answers there.

The hardware in the devices is capable of returning a result far more precise than the API will return it to the programmer. There is programming in the API which filters out sporadic movements and returns a value which is more likely to be something that the user is trying to do. If you're interested in what the actual hardware will do, the hardware in at least one generation of the iPhone is this:

http://www.st.com/web/en/catalog/sense_power/FM89/FM89/SC444/PF152913

You can download the datasheet for as much technical information as the manufacturer cares to reveal.

If you're interested in what the software will do, Apple doesn't publish specific figures on precision or accuracy. Its message is "Try it, see what you get, and that's what you'll get.". The figures for both rotation and accelleration are double-length floating point numbers with '1.0' meaning '360 degrees' and '1.0' meaning 1G so you can't even use the granularity of an integer variable. You can find the API calls here:

https://developer.apple.com/library/ios/documentation/CoreMotion/Reference/CMAcc elerometerData_Class/Reference/Reference.html#//apple_ref/doc/uid/TP40009671

There is plenty of sample code floating around the web for simple programs which just grab this information and show it on the display. For instance

http://nscookbook.com/2013/03/ios-programming-recipe-19-using-core-motion-to-acc ess-gyro-and-accelerometer/