How do I beat a 2000+?

I know this is 9 years later but I too have a Chess Tournament coming up. Not trying to flex or anything but I also have consistently beaten players way above my rating bracket. 500-600 points. I am not kidding lol. I have defeated them in OTB Tournaments Online Tournaments and more. I think the reason I lose most of the time is that I lose my concentration for a split second and blunder a piece or some more. I have a classical tournament coming up and I am crazy enough to register for the over 1700 Bracket. Because Honestly I cant play with 1200s for 1 hours 5 games each.. Any idea of the gambits that I may need to defend against. What will be my strategy?

Thanks

Thanks for your help ✌️✌️🙏👌

Sometimes you can beat them with certain unknown but op openings like English opening,Kings Indian,Sodium Attack and more