OMA vs OME and other issues

Hi, first off.....what is the difference between all these products?

I am getting an error when trying to log into OMA, I can access the web GUI usinghttps://hostname:1311, but am unsure what to type in for Hostname/IP address and username and password...

Second, DRAC works very well on servers so that is a server is frozen I can still reboot it / shut it down, etc. using DRAC, is there a way to do this for desktops? We have fairly new Optiplex desktops (790, 980, 990, 9010, etc.)

Any other Dell tools that would be useful?

How do I get phone support for these products?

Thanks