no such thing as hdmi 1.4 cable etc, its just high speed cable. Hdmi version is the actual port.
Arc just allows TV + apps or whatever connected to the TV to pass uncompressed PCM audio 5.1/7.1 to the AVR. TVs used to rely on optical but this connection could only allow 2.1 uncompressed audio. Some more of the expensive TVs out there may have Dolby/DTS encoders to compress audio over optical but generally most TVs don't to avoid licensing fees.
With ARC you can hook consoles to the TV or run Netflix and get surround sound to the Receiver via Hdmi.