I tried all of the above, but nothing worked, so after a lot of trying i discovered something that ACTUALLY WORKED! I have a Samsung Galaxy Trend Plus phone. What I did:
1) Connect phone with USB charger to your computer
2) Take out battery
3) Press the volume down and center menu button at the same time
4) While pressing the two buttons put battery back in
Your phone will give you a reset mode screen, press volume down, and your phone will automatically reboot itself and turn on:) PS! none of my information or data was lost.