First of all, the
Competition port has been (at least minorly) documented, so that should take care of the Autonomous, Disable, and Channel Select functions of your dongle. Second, one thing to note is the fact that even if you enable manual channel select mode, you need to set the DIP switches on the OI in order to change the channel, and there're certain combinations for the switches in order to use the four available channels (the combinations are documented in the above linked PDF file).
Umm. Information about providing power to the OI through the Competition port hasn't been published by Innovation First, so I can't say much about it, at this point.
Also, what Frank said about providing 1.5VDC to the pins on the Competition port scares me, or, it would if I were on his team. The documentation states that, in order to enable the Disable, Auton, or Channel Select modes, the cooresponding pins should be connected to GND (ground), pin 8. I have made 5 different dongles this year, and every time I never needed any source of power. All of them worked perfectly. Four were used at a pre-season practice event by Ken Leung, and the WRRF, and the other was used by myself, and my team, 258. I wouldn't suggest connecting a AA battery to the system, at all, but if Frank says they did it... well, it's my personal feeling that he and his team were just really lucky.
The same goes for providing power to the OI through the Compeition port. You run the (VERY POSSIBLE) risk of destroying the OI if you guess-and-check this kind of thing. If you want, you can rig up a power supply to provide power through the port on the OI to which the provided AC adapter connects. I would, myself, feel much more comfortable doing this than risking destroying the OI (they really aren't cheap).
If you have any more questions, or would like some clarifications, feel free to ask.