In a press release for a new Boeing "wingman" (BATS) drone being built in Australia, a closeup of this Australian AWACS flying in formation was provided. What would be some of the specific uses for the antenna farm located all over the fuselage?
The image below labels each of the antennas. To summarize based on your groupings:
A: Multi-Role Electronically Scanned Array (MESA) made by Northrup Grumman. It has a similar role to the large rotating dome on the E-3 in tracking airborne targets. Instead of being rotated mechanically, it can be electronically scanned.
B: Communications/Navigation, GPS, ELT (emergency locator transmitter)
C: Missile warning, infrared countermeasure
D: Electronic surveillance
H: Missile warning, electronic surveillance
The large flat antenna along the spine replaces the rotating disks used on older Airborne Radar planes (e.g. AWACS), which physically point at each direction while transmitting and watching for the radar return, and therefore must be spun 360° to get a full picture.
It is an "Electronically Scanned" radar that electronically "steers" the radar beam. In this case, the left and right sides can scan 120°, while the bit on top of the wedge can scan the front and rear 60°, giving a 360° picture.
Airborne electronic warfare systems incorporate a number of different features/modes. These can include searching for nearby (within a few hundred nm) aircraft, scanning for targets on the ground or sea, listening to transmissions by the opposing side, coordinating communications for your side, and possibly even active jamming to inhibit enemy weapons and communications. Different types of antennas will be used for specific frequencies.