How to Fix iphone 4s stuck in dfu mode (troubleshooting)

Hi. i have received this iphone 4s from a friend of mind and that hes brother try to fix this iphone and all he did was mess it up by ripping off the battery flex cable. this iphone would not come out of dfu mode even though if try to restore or use any type of software.
after troubleshooting and removing the battery i found out that the battery flex cable was damaged in a attempt to fix this iphone. the owner fail in this process. now i have the iphone in my hand to fix it correctly. again every iphone has its different issue and different situation.
I will replace the battery and iphone will work again as its supposed to.
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