Rendering 3D objects using .obj file in iOS and adding dynamic texture to touch position

I have good hands on objective-C but not on OpenGl, please help me with the problem below,

I have a human skeleton body as an .obj file. I can display it in the view.

But I faced the following problems

• Rotation around the x, y axis.
• Moving the 3D model relative to any point.
• I cannot detect the touch event of a body part. For example, when I press on my left hand for a long time, the application should detect that the user presses on the left hand.
• Add a marker (any texture) at runtime on the part of the body where the user has touched.

Thanks in advance.