What is the model number (exactly copied from the manual or ID tag on the tv)? I am not familiar with a 38” tv. How old is it? I cannot figure out from what you say how your tv works. I would guess it is pretty old if the video 3 key from the 3000 doesn’t work, and I don’t remember any tv which cycled through the aux input. Usually, you have a separate key to access the aux input, which is not considered a video input, but is another antenna input. I could be way off on this, or I just don’t understand what you are saying.
Discrete codes are codes you can access by using a Radio Shack or OneForAll remote, and will allow you to control functions which are normally on/off (like power) as a discrete on or discrete off command. For discrete codes, see this thread
[Link: remotecentral.com]