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But I'm using Google Chrome right now. How am I able to run the game?

Press on 'Buy', you'll be sent to the shop in which you'll have to buy it with real money. After you buy it, go into a battle, press the '6' key and it will drop.

Why is it for Generalissimos only?
The Number of crystals you get and the number of everything else all depend on your rank. The Crystal Card and the Silver Score Multiplier Pass (30%) are still the same.
What is Spectator Mode anyways?
Getting crystals as a daily reward thing is usually random. I once got crystals as a daily reward two days in a row. I think Tanki Online is planning to change Daily Rewards into Daily Missions. If you complete your "mission of the day," then you'll get crystals and supplies. Or just one of them.