Hello! You can set whether or not a player can view their own disguise by using the player action SetDisguiseVisible. This action can be found in Player Action -> Appearance -> Set Own Disguise Visibility
I believe the consensus on this is client flight speed modifiers are allowed in build and dev mode because of the /flightspeed command. However, client flight speed modifiers are disallowed completely in play mode.
Fortunately, this has been suggested in the past and as far as I know the developers plan on implementing it (It has been accepted in the DiamondFire Suggestions Discord server)
Hello! I managed to hide the healthbar from view in survival mode using SetAbsorption with the number 9999999999
Edit: Please note that setting the number lower, at least my testing, will crash your client
Hello, You can get a full list of code blocks and their actions by going onto node beta and running the command /dumpactioninfo. This will send all of the actions and blocks in your chat as json and you can retrieve it from your logs. Note: it won't show up as a valid command but it will run