Thanks!
But regarding this:
"If no blocks are found on testnet in 20 minutes it will reset difficulty back to 1"
Does also this mean, that difficulty is 1 for the next 20 minutes?
I don't think so.
I think he means this:
So no matter the current difficulty, if no blocks are found within 20 minutes, the current difficulty is set to 1.
Now if someone starts mining using TH/s of power, nothing will stop the difficulty rising from 1.
So it's not forced at 1 whilst people are mining, it's just a change applied once every time the criteria of {no blocks for 20 minutes} is reached.
I hope that explains it a little more.