1. It is just a different means of navigation. GPS is the new toy for navigation and not all aircraft have it yet. The old way is navigating from VOR to VOR or using waypoints.
2. Zulu is the aviation term for Greenwich mean time. So 02:54 Zulu would be like 20:54 Central Time (-6 hours difference), or 8:54 pm
3. Aircraft travel at certain altitudes based on what heading they are going, and whether they are on a VFR or IFR flight plan.
VFR with a heading of 000-179 use odd thousands plus 500 feet (ex 5,500, 7,500, etc)
VFR with a heading of 180-359 use even thousands plus 500 (ex 4,500, 6, 500, etc(
IFR with a heading of 000-179 use odd thousands ( 5,000 7,000 )
IFR with a heading of 180-359 use even thousands ( 6,000 8,000)
Using that format, you can pick what altitude you want. general aviation aircraft usually fly below 12,000, airliners like to be between 24,000 and 36,000, while some of the corporate jets can get up into the mid 40s.
Confusing enough yet, I think I confused myself.
