Click here for this comprehensive CNET article {that is updated frequently} where just about every available command is listed.
Click here for a similar NextPit article "The best voice commands for Amazon Alexa" from Jan 2022.
These range from Basic commands, through those specifically for the Echo Show, and those for the Fire TV and Fire TV Stick, to those for the Fire TV Edition televisions.
You will find that the list has been organised to make it easier to find things - the various commands are grouped under the following categories :-
Media controls
Time and date
Calls and messaging
Purchasing
Notifications
To-do and shopping lists
News and weather
Entertainment
Food and businesses
Math
Settle a score
Definitions and spelling
Sports
Voicecast
Smart home
Bluetooth
Profiles and user accounts
Skills
Cortana
Search
Holidays
Easter eggs.
At home: If you're around your Echo, you can say "Alexa, set an alarm for 6:30 a.m."
Out and about: If you're not at home but want to set an alarm just go to your Amazon Alexa app menu.
Tap Reminders & Alarms > Alarms > Add Alarm. You can also have Alexa wake you up with music.
If home security is a concern you can turn on Alexa Guard before leaving.
Just say "Alexa, I'm leaving" and the voice assistant will start listening for signs of a break-in, like glass breaking. If it hears anything suspicious, it will send you an alert so you can decide whether to contact authorities to check it out. When you return just say "Alexa, I'm home" and it'll stop listening for such noises.
When you're cooking and need to know how many ounces are in 3 cups, just ask Alexa.
You can say "Alexa, how many ounces are in a cup ?" and your Echo will immediately give you a conversion.
Once you have your Amazon account linked to your Echo, you can immediately begin listening to music. However, unless you have Prime or Amazon Music Unlimited, you may run into some songs and artists that aren't available, so it's a good idea to have your other music services linked to your account.
Connect Amazon Music, Pandora, iHeartRadio, TuneIn: In the Alexa app menu, tap Settings > Music and select the music service.
Connect to Spotify, Apple Music, Deezer, SiriusXM, Tidal, Gimme or Vivo: If you're connecting to one of these, tap Link New Service, select the service and enter your login info.
Connect to Google Play Music or iTunes: If you have one of these two music streaming services, you can only use your Echo as a speaker. You will have to manually select the songs you want to listen to on your phone. Go to your phone's settings and turn on Bluetooth. Then say "Alexa, pair." Select your Echo when it appears on your Bluetooth screen.
This one can be fun if you've got no board games and you're trying to entertain friends or kiddos. Alexa has a ton of games you can play, like Jeopardy, Harry Potter trivia, music games, kids games and many more. You can also play multiplayer games with Amazon Echo buttons.
Just say "Alexa, play a game," or if you know exactly what you want to play, say "Alexa, play [name of game]."
Alexa will explain how to play each game.