When running commands in the Minecraft versions mentioned, suggestions are only based on original commands (see screenshot). For example, when typing in a give command as I usually do, "/give @p (or my username) command_block" but in this case, when typing my username, it suggests commands that start with the letter D, such as "/difficulty", and when typing "command_block", it suggests commands containing the letter C, as shown in the image. I believe this is also the cause of many command errors, such as not being able to understand the commands (see the other screenshot).

A note - I have only seen issues with a few commands, but suggestion error on all commands I have tried.

The screenshot below contains a username resembling mine but with some characters or phrases edited.

This bug is also present on iOS devices. Not tested on Android devices.