According to the spec sheet from intel website..
I would like to understand that the max resolution of HDMI interface is hard limit or not. And, If I use HDMI 2.1 will it be able to support higher refresh rate and resolution or not?
I wants to achieve 5120 x 1440@120Hz with HDMI 2.1 to Thunderbolt 3 cable.
Yes, these are hard limits. Your processor only supports HDMI 2.0b output, not HDMI 2.1.
Now, if you are using a TBT port, your output is actually in DisplayPort 1.4 format (this is being converted to HDMI by the cable assembly). In DisplayPort 1.4 output, you can, in theory, achieve 5120x1440@120Hz (see https://en.wikipedia.org/wiki/DisplayPort for more information). Whether you will actually see this after the cable's conversion is the question I cannot comfortably answer as I do not have any information on this TBT-to-HDMI cable's quality, etc.
Note: These results are limited to direct connection of the monitor to the TBT port. If you are using a downstream hub/dock/etc. - especially if USB is also being utilized - then all bets are off.
Hope this helps,
Please remember to not relay only on CPU specs and display specs...
It is very important to confirm what exactly the computer manufacturer enables "to be supported"... Let me explain... I have seen laptops with HDMI 1.4 ports, but the manufacturer "limited" video output to just 1080p 60hz despite the standard supports 4K at 24-30hz.
I have myself a laptop with a processor 11th gen HDMI 2.0, but Lenovo decided to put just an HDMI 1.4 port...
I suggest to check the PC manual before any purchase and review the "video modes" or "supported resolutions" to see the full list