Break days are more for sanity purposes, I would say. You don't have to eat a lot of junk food, just have some good food that you otherwise restrict yourself from for the rest of the week. (I know grammar has gone to **** there, but I'm too tired to care).
yes. you should take break days.
Yes break days are good but I don't see the point if you don't want them. I watch what I eat but always have a blowout or two at the weekend and as long as I'm back on track on Monday I don't gain weight. But I see it more as 'getting away' with having a treat than a deliberate ploy to frighten my metabolism.
You should really be taking two days out per week of your cutting following a plateau in weight loss. But this doesn't mean to eat whatever you want in whatever amount, it means eat at your BMR i.e. don't go over it and don't go under it.
your metabolism isn't going to change overnight
the only "off-day" being beneficial is whereby you are low-carbing, like say 60g/day for 2 weeks
then you have a re-feed day which serves to refill glycogen stores mostly
then you go back
otherwise, stick to dieting at all times, with 1-2 cheat meals not days a week for sanity [if need be]
It's a good idea if you're carb-cycling and don't come off the rails (just eat more of the same stuff).