The game I play (Command and Conquer) uses/requires Windows 7 to operate, will I still be able to play it after Windows 10 is automatically downloaded to my computer after July 29.
Yes, you will be able to play but you will probably need to run the game in one of Windows 10's compatibility modes:
Which game, specifically? Command & Conquer is a game series spanning 17 years of games. Some more precision might be useful.