I have an Archer C9 V1 with Firmware Version 3.17.0

I am in the USA and plan to update my firmware from here:
https://www.tp-link.com/us/support/download/archer-c9/v1/#Firmware

Question 1: If I update the firmware, will that update the Admin interface (which is very old and clunky in Firmware Version 3.17.0)?

Question 2: If I update the firmware, does the latest firmware contain/capture all prior updates, or do I need to update each successive update version in turn, oldest to newest?

Question 3: What Firmware Version number does Archer C9(US)_V1_180125 (most recent version) refer to?  (For instance, 3.2X? 4.5X?)

Thank you