OK, THIS IS MY SUCCESS STORY. I had the worst problem out there, and I successfully managed to come out unscathed, with a special stroke of luck.
My problem:
Had simple swiping on lock screen on my LG nexus 5. My 3G was not working. Called up carrier guys. the jokers said that the settings were fine and I needed to switch off the phone, take the sim out -> switch on -> switch off -> re-insert sim card -> switch on. (yeah, no clue why!)
I did that, and next thing I know, its asked for a PIN. I had no clue what it was! Tried 5 times, asked me to wait for 30 seconds. Kept on trying all logical 4 digit pins I could, started making me wait for every 30 seconds. ADM was not working because...drumrolls...3G was not working in the first place! I hit a dead wall and wasnt really up for the hard reset stuff.
Solution part 1. Making Android Device Manager (ADM) work.
Frustrated fiddling with the locked phone, I had a eureka moment... the settings shortcut panel (the one you pull down by clicking on top bar) was accessible. I couldnt enter main settings listicle though. Tried connecting to a wifi on my laptop...asked for a password which the phone didnt allow me to enter... then I made the hotspot unsecured and tried connecting again, Voila!!! It got connected, and Android Device Manager worked!!! ADM located my phone, made it ring and apparently I could lock the phone first and unlock it! NOT. :-X
Problem 2: ADM couldnt unlock the phone!
Whenever I entered a new lock password on ADM, it said "Google has verified that your phone is already locked so you don't need to enter the password". I was like wtf guys, I know there is a password, I cant remember it and that's exactly I want to reset it!
Solution part 2:
After spending some good couple of hours going through all the forums I saw a definite factory reset looming ahead. People were talking about bypassing the ADM by using findmymobile for samsung phones. Tried it. Didnt work.. of course I had a friggin LG nexus 5! I had almost given all hopes and decided to reset the phone when I saw a small logo near time in the top bar. It was an app called "avast anti-theft" that I had once installed and forgotten." Of course I had forgotten that pin too!
Went to avast anti-theft website, logged in through facebook and then LOCKED MY PHONE.
AND UNLOCKED IT.
VOILA!!! The phone opened! No PIN required. I quickly went to ADM and locked it from there and set a new password. Then on phone, went to settings-> change PIN... it asked me to enter original pin. I entered the new pin. IT WORKED!!!!
So, there I am, with an unlocked phone and a changed pin on a phone whose PIN I had forgotten, whose 3g was not working, a phone that wasn't samsung and ADM being its normal, ridiculous self that it is!
.