Battery cycle can last how count?

Your 2014 has a projected life of 1,000 charge cycles. That's the point that Apple considers it "consumed", or exhausted.
Some users report much longer life (more charge cycles) than the advertised life, but you really can't expect that.

Apple has more information, such as how those charge cycles are computed.

With your cycle number, 57 in (maybe) 2 1/2 years, you might even think that you might have nearly 44 years of use before you achieve 1,000 cycles!
But, no, batteries also wear out due to age. It also might (under some conditions) begin to swell, with your clue that the battery is failing - when it swells through the top of the case.
(Something to anticipate, eh )

But, to answer your questions:
1. Normal max count is 1,000
2. If you charge the battery halfway, you would accumulate one charge cycle the second time you do that (in theory) when you accumulate one full charge.
And 3. No, you don't need to wait for the battery to completely drain. In fact, a full discharge (battery drained) is not a good way to treat your battery.
Most experienced users will offer the opinion that you should use your MBAir. Use it on battery, if you like. Plug it in when you want to. Many will let battery go past the low battery warning (where it goes to sleep by itself) once every month or two, then let it fully charge. I call that "exercising" the battery.
It's a portable, and designed to run on battery. Do that occasionally.
That's it...