"can u pass a card through a window like criss angel" yea i do kaos
I don't think this approach is a very good idea. Once you accept their challenge you are then performing on their terms.
This process could just continue. Once you pulled a card through the window you could just get something else like 'can you walk on water like Criss Angel'.
"This is magic...not miracles"
I think this is a great line, you acknowledge what they say but make a joke out of it and you're still in control of the performance.
If anybody asks me if I can do something like a levitation I just say no and offer to show them something else. If they persist with asking me to do something I can't I just stop performing.
You need to politely make it clear to them that you're not their trained monkey that does whatever trick they want whenever they want you to.
Although I rarely get these questions, while I never actually state it I make it quite clear that my magic is purely sleight of hand and is skill based. When the audience knows this it's unlikely that they will ask me to levitate.