"What is chin strap and it's purpose?"에 답변The chin strap is beneath the bottom edge of the display, so the display doesn't rest on it. It seems intended to hold the EMI (electro magnetic interference) black strips that surround the inside of the iMac.
"What is my Logic Board EEE code and/or where is it located?"에 답변Mayer is right (as he always is): just to add that in the last EEE codes I'm seeing, it's the first 4 of the last 6 characters in the apple serial number (the one sorrounded by *, example: *C94439700CCFVNYAY* so the EEE is FVNY. Not sure this is always like that, but is what I'm finding lately. Cheers!