A: Yes. You can purchase just the Receive and Transmit cables separately or you can purchase the whole cable set.
A: The RX I/Q cable adapts the RX I/Q port to a standard 3.5mm plug so that you can use the soundcard in your computer to process the signals needed for any of the new SDR programs. You can purchase just the individual cable or the entire KX3-PXKT to obtain it.
A: The ACC2 Module cable exposes the KEY OUT signal that is needed to enable a linear amplifier to go into transmit when the KX3 does. The RCA jack you see on the module is the KEY OUT signal formatted into an RCA jack that is commonly used with my popular linear amplifiers, including those from Elecraft.
You can purchase it separately or as part of the KX3-PCKT cable kit.