I am not able to see specific protocol version of HDMI (1.4 or 2.0) supported by RPI 3.0. Basically I want to take HDMI 2.0 output from RPI and provide it to my device.
Also can we measure the rate of output HDMI signal?
Since RPi 3 uses BCM2837 SoC, you're out of luck:
BCM283x supports HDMI V1.3a.
Not sure what the "rate of output" means, but HDMI 1.3a runs at a frequency of 340 MHz and a data rate of 10.2 Gbps. No need to measure that.