1. Do I need to install it on BungeeCord?

No
1. Only need to install on each sub-server and configure the following in config.yml
# Sub-server identifier, must configure this first for proxy servers (/server lobby) for teleportation
server: "lobby"
2. Configure to MySQL mode

2. Common PlaceholderAPI Variables

Enter the following commands to install PAPI extension components (choose as needed)
papi ecloud download player
papi ecloud download vault
papi ecloud download server
papi ecloud download Multiverse (multi-world v4 version optional)
papi reload

3. Can't receive messages after manually adding a channel?

Except for the default channel, other newly added channels require giving players corresponding permissions

playerChat.chat.channel_name to receive messages

Chat channels registered by third-party plugins do not require permissions (handled by the third-party plugin)

4. Duplicate messages appear after installing the plugin?

If you have CMI installed at the same time, just disable CMI's chat feature

Path to disable CMI chat:
plugins/CMI/Settings/Chat.yml

Set the following two to false
Chat.ModifyChatFormat: false
Chat.ClickHoverMessages: false

5. How to configure RGB colors?

Configuration format: &#FF0000 example
or
3.x+ can directly use MiniMessage format