2 Peter 1:20
knowing this first: that no prophecy of the Scripture is of any private interpretation (King James Version)
[I think this says no prophecy of the scripture is interpreted privately. Maybe in one's own privacy or in private. Not sure.]
this first knowing, that no prophecy of the Writing doth come of private exposition, (Young's Literal Translation)
[This could mean no prophecy of the writings in the bible comes from a private explanation. Possibly so.]
Above all, you must understand that no prophecy of Scripture came about by the prophet's own interpretation. (New International Version)
[Here it could mean no prophecy of the scriptures can be based on what the prophet understood it to mean, or something like that.]
But you need to realize that no one alone can understand any of the prophecies in the Scriptures (Contemporary English Version)
[This sounds simple enough. No one alone can understand any of the prophecies in the scriptures. No one alone. So maybe if we are more we'll be able to understand the prophecies. Wait, there's a verse that says something about a testimony being established in two or three witnesses. Maybe that what this verse means]
Above all, you must understand that no prophecy in Scriptures ever came from the prophets themselves (New Living Translation)
[Clear enough. No prophecy ever came from the prophets themselves. They came from somewhere. Hopefully from God. I understand that, I think.]
with this most clearly understood, that no prophetic Scripture can be explained by one's unaided mental powers (International Inductive Study New Testament)
[I think this one is saying no prophetic scripture can be explained by one's mental powers, unless he is aided by something, hopefully the Holy Spirit. But it doesn’t say so maybe I'm guilty of adding to the Word.]
We definitely need Spiritual discerning of God's Word.
May His Spirit guide us