In order to see different demos of how a stage is played out in Ikaruga, change the monitor type settings before going into demo mode. The different settings will show these types of demos:

Vertical 1&2: These settings will show increased difficulties.
Horizontal 1: This setting will show beginning tactics.
Horiztonal 2: This setting will show more advanced tactics.
Horizontal 3: This setting will show advanced tactics or bullet eater tactics.