iPod Touch 4th Generation Front Panel Replacement
Glue is under the black part of the glass, not under the clear part of the glass.
The Glue is mostly around the top and bottom about 1/2 inch in or so, around both left and right edges the strip of glue is very thin about 1/8 inch or so.
I had success with heat and sliding the tool or pick up and down the side where there is less glue until it started separating being careful that I was between front glass panel and the black plastic bezel.
iPod Touch 4th Generation Upper Logic Board Replacement
Use extreme caution when lifting the board. There are 2 ribbon cables that are extremely fragile, 1 connecting the rear facing camera and another connects the volume controller flex on the logic board.