Unleaded or premium for 2014 lexus is250

So i have a question. I know that Is250 requires premium fuel. but.i have also seen people say that if u start putting unleaded fuel, the computer is gonna adjust to that fuel over time even though the performance is gonna be a bit down.

My question is, is it true? also putting unleaded do any major harm to the car mechanically?

if there is anyone whos been putting unleaded instead of premium, I would love to know your experience too..