I finally solved the issue regrding the auto filling of the log in and the non functioning letter "z" key. I followed the below link on how to do a clean install of the OS X Maverick and created a bootable hard drive. Note that an 8gb thumb drive isn't enough. I was able to made 2 partition on my 500gb external HD. I alloted 20gb for the OSX installer and the other partition I am using for the back-up of my macbook pro.
Here are the links:
How to clean Install OSX:
http://macpaw.com/support/cleanmymac/knowledgebase/how-to-clean-install-os-x-mav ericks-on-my-mac
How to make a bootable HD
http://osxdaily.com/2013/10/23/create-os-x-mavericks-install-drive/
Again, I used an external HD.
Also, before you perform the installation of the OSX.
Make sure you format the Macintosh HD where you will install the downloaded OSX.
What I did was from, restart, I pressed command R and went to Disk Utility and formated my Macintosh HD which is where you will install the new OSX.
Right after I was able to successfully installed the OSX I only downloaded the apps I needed. Then I made a back-up of my macbook via time machine. Now i will always have fresh back-up in case this happenes again I will just re-imstall the 1st back-up via Tome Machine.
I hope this will solve your issue as it did mine.