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Can confirm in 23w51b, in Singleplayer, survival mode or creative mode. Item duplication seems to only occur in creative mode.

Duplicate of MC-263062.

Duplicate MC-261638.

Can confirm in 23w51b.

A working command that can reproduce this bug: /give @s netherite_sword{display:{Name:'{"text":"click me!","clickEvent":{"action":"run_command","value":"/give @s diamond"}}'}}

I think what this reporter means is:
When a player dismounts a horse, it creates an upward momentum that makes the horse look like it jumped.

Can confirm in 23w51b.

Can confirm in 23w51b.

A duplicate of MC-140276.

Same issue as MC-186086, but a bit different.

Confirmed in 23w51b. 

If you do not use the tick command, it should not break anything.

You also need to attach some files to reproduce the bug (for example, the data pack you are using, a debug by /debug command).

Can confirm in 23w51b. A similar behavior was observed for the mobs on a larger scale attribute.

Can confirm in 23w51b. Caused MC-262864.

That's because 2 items have the same attribute modifier UUID. Try to use loot tables or add attribute with a new UUID.

Maybe a duplicate of MC-125936.

I think you should read update logs.

Minecraft Java Edition 1.20.3

Check pack.mcmeta: Data pack – Minecraft Wiki (Link to unofficial Minecraft Wiki)

Can confirm in 23w51b.

Can confirm.

Wait, this is a duplicate of MC-197139.