This looks like typical backlight damage from water. Best bet to replace the entire LCD assembly and sell the old one on ebay. Trying to replace just the backlight layers is near impossible. Also i am almost positives it is the same LCD as the late 2013 & Mid 2014 A1502 Retinas.
What you should check is it the computer will charge the battery?? Also you really should take apart the computer fully and remove the logic board and IO board and make sure there is no corrosion on them. After that you might be lucky and have a working computer again that you should keep away from liquid.
Most things are fixable but its a question if you have the tools and knowleage to fix them. What you would want to do is first run the board through an ultrasonic cleaner to remove all the corrosion. Then you want to get the schematics and board views for the board and begin testing every power rain the the machine. Once you find what rails are missing you will then need to trouble shot the circuit for that power rail and find the problem components and replace them.
Alright if you really need all the data off the computer i would recommend sending the computer to someone who can repair the logic board rather then trying to fix it yourself and risk losing everything. As the SSD is soldered on and you would need to unsolder it from the first board and solder onto a second all requiring very good quality and expensive hot air stations. Sorry this probably isnt what you wanted to hear but its going to be your best bet to get all your data.
Your OS password or a EFI/Bios Password. If its an OS password it can be reset easily by either reinstalling OS X or Pressing command and R on startup and boot into recovery, Next go to terminal under utilities then type "resetpassword" enter the password you would like for the account and confirm. If its a EFI/BIOS password you will either need to take to apple or flash a new bump to the chip