Finish all levels and complete all stories (metas).
After your final level win, the Grand Mode pop-up will appear.
You can:
Complete All Stories – instantly finish all remaining metas and claim rewards.
Do It Manually – finish metas one by one as usual.
Once stories are complete, tap Enter to join Grand Mode.
What changes in Grand Mode:
Main menu turns purple.
Level button becomes green with a purple frame and shows “Round *”.
Meta button changes to the Grand League button (if entered before the last hour).