iPad 4 front panel was broken.
First, I followed the iPad 4 front panel replacement guide in the iFixit.com. My method was not different largely.
1. I used hot wind gun instead of the iOpener. Then you can blow the panel about 15 seconds for loosen the adhesive film.
2. When you lift the front panel, you must care of the home button flex cable. It is so weak and can be tear easily!!