To fix scrren lock issue, do the following:
For ALL whoever are facing problems with the LOCK SCREEN here is the solution :
Tools Needed:
1. Root Explorer or Solid Explorer
Steps to restore:
1. Using root explorer locate the /efs/imei/ folder. In that folder there should be a file called keystr. In my case the file was missing which is why the lock screen was missing and was causing my problems.
2. using root explorer create a new file called keystr
3. also in root explorer open the file keystr in text editor and type ON
4. now go into hex editor and locate the /efs/imei/keystr file.