I implement the app thinning in my project by getting the reference from below two answers:-
To expand upon saswanb's answer, the pathForResource you use has to match the folder or filename you added to the ODR tag. If you add a reference to a folder to an ODR, you can search for that folder name, but not the contents of the folder.
NSString *path= [[NSBundle mainBundle] pathForResource:@"ODRFolder1" ofType:nil ];
But if you add the contents of the folder to the ODR tag, then you can search for each file individually.