First, welcome to FT!

Second, four flights allowed in each visited continent except N. America (six.) Only two stopovers (>24h) allowed in continent of origin.

One flight number = one coupon. If you find a "direct" flight (e.g. LGA-RNO) that has an intermediate stop (e.g. DFW) but doesn't change flight number, then it's okay. Otherwise, one coupon per takeoff/landing cycle.