color - How should artwork be setup for T-shirt printing?

1. 
   

   What does it mean to colour separate the artwork for T-Shirt printing?

   
   
   


2. 
   

   It is normally suggested to use Pantone colours for T-Shirt printing. Is it the Pantone Coated or the Pantone Uncoated? The Uncoated one has more subtle colours and we can't choose brighter shades if the design requires that. What is more appropriate for printing?

   
   


3. 
   

   Can we use gradients in T-Shirt printing or is it suggested to stick to flat colours only?

   
   

The reason for asking if gradients were ok was to use it as an option for this design:

I was considering it an option, as it will be difficult to colour separate since the textures are clip masked inside the lion.