To tell which version of firmware, use the 983 command: 1) Press Setup until 2 blinks 2) Enter 983 3) Press the "1" button and count the number of blinks. No blinks means 0 4) Repeat step 3 using buttons "2" through "5" Steps 3 and 4 should yield in succession each digit of the signature.
Old FW has signature 25764, and new is 25761.
Acpgz file is just a compressed file. It ordinarily will automatically expand to the uncompressed settings.bin file. You then copy this file to the remote which acts just like a USB thumb drive. On my son's Mac, it showed up on the desktop as a folder titled VOXX4REMOTE.
For some reason, the simpleset.com website doesn't have the actual manual. You can download it from hifi-remote.com. Note however that the manual doesn't describe the 9XX commands which can be used with the remote. For example, the manual tells you how to assign a macro to a digit button which will only run if the remote is in the device mode for which the macro was defined (frequently termed a Device Specific Macro). One can also use the 995 command to assign a Global macro to most of the buttons which will run in any device mode. The remote doesn't allow assigning EFCs or macros to the device buttons or Combo buttons, and 995 Global macros can't be assigned to the digit buttons.
Regarding how you would like the remote to function, realize that we have to take into account the behavior of the Vizio. Will it accept a discrete HDMI3 command immediately after being powered on? Will issuing the HDMI3 command turn on the TV? I expect that most models of TVs on power up will remember which input was last in use. Is that not true for the Vizio?
Also, from your description, I guess that the remote wasn't actually successfully programmed to issue the HDMI command--otherwise I suppose that the Vizio would only cycle through the HDMI inputs, and none of the others. You should be able to get the OARUSB04G to do whatever the OEM remote does with its HDMI button. Try reassigning it (or try the HDMI1, 2, or 3 discretes). Make sure that the remote blinks twice when step 6 is competed. A single long blink means the EFC wasn't accepted.
Let's get all of the commands working before trying to choreograph th estartup of the system.