Lock the fix area of the Dock.
defaults write com.apple.dock contents-immutable -bool yes
defaults write com.apple.dock size-immutable -bool yes
defaults write com.apple.dock position-immutable -bool yes
killall Dock
Setting recent application number, default is 3.
defaults write com.apple.dock show-recent-count -int 5;
killall Dock
More modern macOS can not stop upgrade from setting, but still can clean the red dot.
defaults write com.apple.systempreferences AttentionPrefBundleIDs 0