001 I downloaded the rig, and when I open it, there is no skin
You're going to need to install the rig. To do so, find wherever your Cinema 4D directory folder is. If you have the program installed in its default location, it will be located (on Windows) under C:\Program Files\MAXON\Cinema 4D R__\. If your program is not installed there, it is likely somewhere else. If you need to find it, find wherever your "CINEMA 4D.exe" file is located, and it should be in there. Within your directory, there should be a "library" folder. If there isn't, create one. After that, open it, and take the "FMR _.lib4d" file and drag it into the "library" folder. Open Cinema 4D, and within your Content Browser, you should now have FMR there. Open that, and double click to add in the rig. This will be here whenever the program is re-opened, and textures will transfer between files.
002 When I try changing the skin on the rig, nothing happens
This is a problem that occurs whether you are using an outdated version of the program, or not using the proper copy. For my rigs to work properly, you will need Cinema 4D Release 13/14/15/16. Along with this, you will need to be using a Studio version of the program. To find out if you are using one or not, at the Menu bar of the program (at the very top of your screen) go under Help>About... and it should be listed. If the version you are using is Prime, Broadcast, or Visualize, you will sadly need to upgrade to Studio for everything to work properly.
003 I want a "WeedLion square mouth" on FMR, I see others with it, how do I get it?
Though anyone is free to edit the rig and add it themselves (it is against terms to redistribute this edited version) I have done edits to add a square mouth onto the rig for certain people. Basically, I do not do them by request, so asking me for the edit will not get you the edited version. The reason it is not on the rig is because this is a perk of WeedLion's paid rig, and I do not feel that it is right to add that onto a free-to-use rig. No matter how old it may be, it's still not mine to decide, so whether you may respect this decision or not, it has to stay that way.