so i dont really do much in terms of cake the only cakes i make usualy are single layer or crumb or bunt type cakes.  I saw this photo of a cake that looks super easy to make 

its a cake that is frosted in buttercream then has ganache on top that is dripping down the sides of the cake  simple cake i figured i could pipe around the bottom and top maybe sprinkle the sides or on top maybe a few waffle cones pieces dipped in chocolate on top 

i have the deep 9 inch wilton pan i was thinking making two cakes in that cutting them in half so i would have 4 layers i would fill each layer with chocolate mousse ice in white buttercream and then do a semi sweet ganache or bittersweet ganache on top  for a cake that size would i need any type of supports?

its a birthday cake for my dad and not a cilent so  dont have to have it super perfect but i dont want it to fall apart in transporting it 

If it's a single tier you don't need any supports.

Yes, a single tier doesn't generally need supports unless it's more than 6" high.

yes it it will be a single tier 4 layers i am doing two cakes in the wilton deep round pan i think its 9 inches its the pan that a whole box of cake mix will fit and bake into it 

also should i let the cake crust before putting the ganache on top i dont want to melt the buttercream with the chocolate or should i let ganche get to room temp but still pourable