https://beta.apple.com/sp/betaprogram/restore#ios
please read it carefully it helped me fix my 6s that was stuck in dfu mode for 3 days don't download any other app's besides the apple verified ipsw's,
- make sure you're device is on.
- download the ios 10.3.3 ipsw
- wait for it to finish
- press the option key ( alt ) hold it and click on update phone with the mouse
- when finder shows up click on the recently downloaded ipsw or search it up in the search bar
- wait for itunes to verify the ipsw
- wait for you're iphone to verify and install the update
- and you're back on ios 10! how ever if you wanna go back to 10.3.2 visit ipsw.me download the ipsw and repeat this same process
- btw ios 10.3.2 is the only oldest apple veriefied ipsw so dont try to download any other lnk
