2. "descending across Spica(?)" "at Spica(?)"
Good answers for your other two questions, but some clarification on this one. What you are hearing is an altitude "crossing restriction", SPICA is just the fix representing a point in space that ATC uses to reference the crossing restriction and it happens to be on the SPICA 2 arrival. on that STAR the exchange sounds like this:
ATC: "Delta 212, cross SPICA at one two thousand feet"
Pilot: "cross SPICA at 12 thousand, Delta 212."
There are MANY different ways a crossing restriction can be issued, however, and they often are not at any waypoint or fix. in that case ATC will still reference a waypoint on the flight plan with a distance associated. they often also include a speed restriction that must be complied with upon crossing that point in space:
ie. "Cross 35 miles west of DAIFE at one-zero thousand, 250 knots.
Just to make things even more of a pain in the A$$, lazy air traffic controllers have now come up with "Optimized Performance Dececnt" STAR. an OPD STAR will contain multiple, often MANY, altitude and speed restrictions as part of the procedure, however instead of ATC having to manage the aircraft and individually clear each stepdown, they now issue a clearance to "Descend Via" which then shifts the burden to the crew to ensure making ALL restrictions in the procedure as depicted on the STAR plate (this skyrockets the cockpit workload exponentially and often leads to task saturation but that's a different conversation) ....AND they can also add caveats to the procedure during such a clearance:
ie. " United 1105, Descend Via the Freedom 3 Arrival, except maintain two one zero knots"
P.S. Detroit Metro does not currently have any OPD STARs so you likely wont hear that listening to them.
Anyway, hope that gives you a better handle on what you might hear.
