[quote]Why did the Prophet of Truth need Johnson to activate all the Halos?[/quote]Only a reclaimer or Forerunner can activate Halo. [quote]It's because only humans can right?[/quote]Correct. [quote]Can Covenant access Forerunner tech now?[/quote]They always could. Only certain installations with a certain importance were restricted to Reclaimers and Forerunners. Typically military installations. [quote]How are humans able to and why?[/quote]Only humans with Reclaimer status have special access to Forerunner devices. This was done to assist humanity on their path to the Mantle and give them access to their legacy.