For emulation
cdi format yes
self bootable required yes
gdi format yes (but region setup must match the gdi image/GDI is a raw dump of the original GD-Rom media)
Utopia is useless
For NullDC grab the latest version 1.0.4 r150 from
http://www.epforums.org/showthread.php?66669
You will also find a link to the homepage of demul that is the other Dreamcast emulator that you can use
Note Dreamcast emulation is far from perfect just yet though, but the GameCube had a few ports of Dreamcast games like Evolution Worlds
There is also another Dreamcast emulator but you do need the developer version of C++, the emulator is Reicast that was originally designed for high end android devices