New tank setup questions

Hi,

I would like to set up a tank I have mainly to grow corals and maybe anemones.

The tank is:

24x18x12
19 Imperial Gall
22.5 US gal
85 ltr

I know what I am going to do for filtration and lighting, but I'm not sure about the following:

1-Should I have a substrate? If so what should I use and how deep?
2-Does it need live rock?
3-Would it be okay to just put the frags on the bottom or should I put in a plastic grid to raise them all up?

Thanks