There is a setting in the config files to make the chickenchunk's chunkloader only stay loaded while the player is online. If that is enabled and you log off, those chunks would be unloaded even if your friend was online elsewhere on the server. If it's disabled, then even while you are offline the chunks will remain loaded, so anyone's objects will continue to work in those chunks.
The radius option counts from the chunk the chunkloader was placed on. So a square with a radius of 1 will load a 1x1 area, in other words just the chunk it is located on. A radius 2 will do a 3x3 area, centered on the chunk the chunkloader is on. Radius 3 will do a 5x5. Radius 4 will do a 7x7, and so on. The maximum chunks that can be loaded is also specified in the config file.