As far as 1, I got it directly from King of Fans because Home Depot would get a few and sell out quickly.
2: It is just the same as your regular remote control that comes with the module. You have to address all 3 with the dip switches. There was talk that these came out a bit wider than the Decora openings. I installed one a couple weeks ago in a 3-gang switch and used a 3-gang Decora cover without any issues. I wish these would be mains powered but they are battery.
Also, the tip about using a clear dot over the light button is a good one if you want to feel around for the light in the dark. The link for the remote is here: https://www.homedepot.com/p/Hampton-Bay-Universal-Ceiling-Fan-Wireless-Wall-Control-68109/205846346
When I rewired my home, all ceiling lights were placed on the same circuit, away from the wall receptacles. I ran 12-3 from each ceiling box to the wall switch. On the dumb switch and fan, black was mains, white was return for light and red was return for fan. Because resetting this module requires on/off sequences, I tied the black and red together in the wall and left the white open. In the ceiling, I fed the hot to that black wire and the red return to this module. That way, should I ever need to do the on/off sequence, I remove power, temporarily install a normal switch, then restore power and then do my on/offs. This keeps me from having to do it at the panel and do the on/offs for all fans. Once it is fixed, pull the power and remove the switch, and put everything back. These remotes are shallow enough you can leave the wire behind it and wire nut’ed.
3: Yes, you would need a Zigbee device, such as a SmartThings hub for Alexa or Goggle Home to be able to turn on or off the light and fan. Since the modules are AC powered, they also act as Zigbee repeaters. Just make sure at least one is close enough to the hub, and the rest are within range of the others. Zigbee is not as far reaching as Z-Wave or WiFi.
You will need to have the SmartThings (or whatever hub you use) skill in Alexa or whatever Goggle home uses.
When you get your fans joined up with the device handler and the child devices install, you can run a device discover to get Alexa or Google to learn about your new devices. Then, Alexa will know the devices. They will be several new switches. For instance, my living room ceiling fan:
Living Room Ceiling Fan
Living Room Ceiling Fan Light
Living Room Ceiling Fan High
Living Room Ceiling Fan Med-High
Living Room Ceiling Fan Medium
Living Room Ceiling Fan Low
Living Room Cool Breeze
Saying any of those turns on the light or the fan speed. I use “Alexa, turn off Living Room Ceiling Fan” to turn off the fan or “Alexa, turn off Living Room Ceiling Fan Light” to turn off the light. Telling it to turn On any of those does that. Depending on if you have dim-able bulbs and have set the module to know it has dim-able bulbs, you can even ask, “Alexa, dim Living Room Ceiling Fan Light to 50%” and it will.
There is a whole topic about this. I would refer you to this for more information.