you cant
Command blocks can only be obtained using the give command and can only be successfully used by server operators in creative mode.The command block will perform certain commands when it receives a redstone current, these commands can be set by right-clicking on the block.
the possibilities for commands is endless in bedrock edition as long as you know how to add your own custom commands using command blocks which you can get by typing /give @s command_block
To create an arrow barrage in Minecraft using command blocks, place a repeating command block set to "Always Active" and use the command /execute at @e[type=arrow] run summon arrow ~ ~1 ~ {Motion:[0.0,0.5,0.0]}. This command will summon arrows above each existing arrow, creating a barrage effect. You can also adjust the Motion values to change the trajectory of the arrows. Make sure to set a chain command block to execute after it, if needed, to enhance the effect or control the barrage's duration.
In Minecraft 1.5.2, you can use command blocks to give players powerful armor by using the /give command. For example, to give a player diamond armor, you can use the following commands in separate command blocks: /give @p diamond_helmet /give @p diamond_chestplate /give @p diamond_leggings /give @p diamond_boots These commands will provide the nearest player with full diamond armor, which is considered overpowered in the game.
If you're using WorldEdit. The command is, /tree redwood
To give a player jump boost using command blocks in Minecraft, you can use the /effect command. Place a command block and enter the command /effect give @p jump_boost 10 1, where 10 is the duration in seconds and 1 is the level of the effect. Activate the command block with a redstone signal, and the player will receive jump boost for the specified duration. You can also use a repeating command block for continuous effects.
In Minecraft, you cannot obtain a spawn cage directly as a player item; spawn cages are part of the game’s structure for mob spawning. However, you can create a similar effect by using a command block to generate a specific mob spawner. To do this, use the command /setblock ~ ~ ~ minecraft:spawner{SpawnData:{id:"minecraft:[mob_name]"}}, replacing [mob_name] with the desired mob type. Make sure you have cheats enabled to use command blocks.
You can fill the up with blocks or you can collect it using buckets.
Leaves can be harvested using Shears on a tree's leaf blocks.
Unfortunately, using the /give command will only give you a pig spawner.
You cant find a giant mob in vannilla minecraft but you can sumon him using a command or a spawner.
you cannot craft one, you will need to make it using your imagination using blocks etc