MacBook Pro won´t let me log in after PRAM
It seems like the main issue to address here is being able to log in again with a valid password. Once you've done that the rest can be sorted.

Since you've got a late 2011 MacBook Pro, you should be able to use these steps to reset your password from Recovery Mode:


Power off your MacBook Pro
Boot into Recovery Mode by pressing the power button while holding down CommandR
If prompted, select your language and press enter
Choose Utilities > Terminal.
Enter resetpassword (all one word, lowercase letters)
Press Return
Select the drive with your account (typically the main drive)
Choose your account using Select the User Account.
Enter a new password 
Re-enter the same password
Enter a password hint
Click Save 
Ignore the warning about the password changing
Click OK.
Shutdown the Mac using Apple > Shut Down
Restart your MacBook Pro normally and use the new password to log into your account


Let me know if this doesn't work.