AdafruitADXL335 Triple Axis Ready Accelerometer

Can I apply 3.3v on the 3v pin to power the device?

Just to make sure, will his device send constant differing voltages (linearly) as it is subjected to different G forces from -3 to +3 G's?

Can this item detect whether a stationary object - like a platform or table top - is level?

The adxl335 has 7 holes then why does the header strip have 8 pins? one of them cannot be soldered on the board.