AccutireTire Pressure Gauge Tread Depth Gauge

Did this item come with a battery? and if not, what type does it use?

does it read the depth in 32' or MM. one reviewer (T. Singh, December 23, 2014) claims in MM not Inches

The pressure gauge can be seen at night. It has an illuminated display

What degree of accuracy is the gauge in (+/-) psi or depth (in)? no astm or asmi certification so are we suppose to take accutire word.