Hunting for the third and final GM norm for a year now, Grover crushed Cori who played with white. The Delhi-based had made his second norm during the last World Junior Championship at Chennai, and repeating the same feat here puts him among the best junior players of the world.
Grover`s splendid result was a huge boon to the Indian contingent here and International Master Debashish Das made it a rare Indian double of GM norms by holding Grandmaster Niclas Huschenbath of Germany to an easy draw.
For Das, it was the maiden GM norm and he will have to make two more norms to become a Grandmaster.
For Grover, it was a delightful day as everything went according to his plan. The Indian came up with an opening surprise by opting for the Grunfeld defense as black, something he had never done before and even as Cori quickly played the opening moves, he drew a blank in the early middle game.
By move 16, both players had spent little time after every move thereafter the time difference grew as Grover had worked out his strategy at home in perfect fashion.
The outcome of the game was clear by move 25 and Cori, the fourth youngest Grandmaster ever in the history of the game, conceded defeat.
For Das, it all happened swiftly as he knew a draw was enough. The English opening of Huschenbeth did not yield desired results and his attempt at an attack on the king proved futile in the middle game.
Das was forcing a draw when Huschenbeth decided to part with his queen and forced repetition of moves.
With the huge Indian party, there was a lot of fighting chess at the top of the tables too. Richard Rapport of Hungary defeated second seed fancied Chinese Yu Yangyi to grab the sole lead on 7.5 points. The Hungarian is now followed by Aleksandr Shimanov of Russia,
Alexander Ipatov of Turkey and Conrad Holt of England who all have seven points apiece while Grover and Das are now sharing the fifth spot on 6.5 points.
P Shyam Nikil continued with his comeback attempt and outplayed Callum Kilpatrick of England to notch six points in all but the other Indians seems to be slipping away from the race for a podium finish.
GM-in-waiting M Shyam Sundar split the point with Evandro Amorim Barbosa of Brazil, Aravindh Chithambaram lost to Aleksandar Indjic of Serbia and Norwegian Frode Urkedal drew with Diptayan Ghosh.
Lower down too, Anwesh Upadhyaya and Nishant Malhotra could only manage draws.
In the girls` championship being held simultaneously, Bhakti Kulkarni played out a draw with with Jovanna Vojinovic of Montenegro to reach six points out of a possible nine.
Pon N Krithika succumbed to another defeat to remain on four points while Ivana Maria Furtado inched herself up to 4.5 points defeating Megan Owens of Wells.
The lead here is now shared by Gup Qi of China, defending champion Deysi Cori of Peru and Meri Arabidze of Georgia who all have seven points apiece.
Four more rounds remain in both championships that decide the best under-20 player in the world.