You must have SLOT MACHINE and ROULETTE WHEEL to make GAME BLOCK. You can find this item in special category. Using growspray would be madness, better get a time machine. Good for hogging some experience if it is farmable. There is no data about durability. Unfortunaltely seedratio information is not available. Oops, there is no entry in the database about gemratio. If you know something, please share. Currently we do not yet have knowledge about the blockratio of GAME BLOCK.