Bedrock Developer Beta

The Bedrock Developer Beta is a beta version of Bedrock Edition accessible only by developers and marketplace content creators. There hasn't been much documentation of the version.

Leak
The version was discovered and leaked by multiple sources, notably by a user known as TantalusC, and was showcased by a YouTuber named Element X, alongside the 1.18 Developer Beta which included the unreleased fireflies and bundles. He received an email from Mojang Studios associates asking him to take down the video, threatening legal action against him, and the video was later taken down.

Notable Differences
This version has additional development features intended to aid developers.
 * A Java-like F3 screen
 * Advanced settings for terrain generation and weather
 * Slowing down the time
 * Viewing hitboxes
 * Various graphs

Commands

 * aicreate
 * aigoals
 * aistop
 * audioaction
 * automate
 * bhave
 * bossbar
 * bounds
 * camera
 * changedimension
 * Likely changes the dimension you're in. (for example, going to the nether from the overworld)
 * cheat_ability
 * cheat_movement_debug
 * cleanroom
 * clearloadedstructures
 * corruptworld
 * crashclient
 * crashserver
 * debugcamera
 * debugprofile
 * destroyblock
 * dumpblocknames
 * dumpblockpalette
 * dumpentitiesclient
 * dumpentitiesserver
 * enchantrandom
 * equip
 * fillchestblock
 * filldrive
 * filllevelstorage
 * findanchoredbuildpos
 * findflatarea
 * findnearbypickup
 * fixbiomes
 * fly
 * Likely makes you fly.
 * getblockname
 * getchestcontents
 * getdurability
 * getexperience
 * getmobdebuginfo
 * getpower
 * getselecteditemcount
 * getstructure
 * getworldname
 * health
 * hunger
 * insomnia
 * islargechestblock
 * isplayercrouching
 * isplayerflying
 * isplayergrounded
 * isworldloaded
 * kit
 * leaveworld
 * Likely removes the player from the world.
 * loadbehaviortreedefinitions
 * lookat
 * me
 * memwarn
 * mixer
 * mobinfo
 * navigate
 * nearbyentityisbaby
 * notifyprofiler
 * option
 * particlelegacy
 * paths
 * pause
 * placefeature
 * placefromhand
 * placestructure
 * playerstat
 * postrackclient
 * postracksrv
 * profile
 * raid
 * record
 * redstonetest
 * register3pserver
 * reloadanims
 * restart
 * resupply
 * rot
 * savestructure
 * scheduler
 * selectinventoryitem
 * sendmodalform
 * sendshowstoreoffer
 * serverinfo
 * showallitems
 * showfrustum
 * simlock
 * simscale
 * skin
 * spawnfeature
 * spawngroup
 * spawning
 * spawnitem
 * spawnmob
 * Likely spawns any mob into the game.
 * spreadplayers
 * stest
 * stopsound
 * Likely mutes the game.
 * stoptime
 * Likely stops time.
 * systemstat
 * test
 * testassets
 * testfor
 * testforblock
 * testforblocks
 * timelock
 * title
 * titleraw
 * tpb
 * tptobiome
 * Likely functions like the locate command, but teleports you to the biome directly instead of giving you coordinates to it.
 * tptosuitabletree
 * transferserver
 * uidebug
 * videostream
 * videostreamaction
 * wipeout
 * wsserver