Most of the bot's functions have changed in the latest update. Most have been migrated accross, however some will require some migrating from you.
All commands have been moved to slash commands, or context menus. For message related commands see the message management docs and for config related commands see the config docs.
The new version requires messages to be stored in the bot's database.
This was not previously done.
To add messages to the bot, first attempt to edit a message (through the actions context menu), then it should send an error with further instructions.
The bot should add a new context menu that you can use to add a message,
Previously there was the concept of one role required for message actions. This is now a much more complicated system, see the permission docs for more info on that. Previous admin roles have been set as the message management preset on the new system. This means that that role will be able to send, edit, and delete messages sent via the bot. If you don't want this to be the case, please the permissions for that role.
This has not changed, other than what is sent to the channel.
Prefixes have been removed, and are no longer used.