1. Runways are numbered according to their direction, in detail the rwy magnetic bearing or QFU. Divide mag heading by 10 round it to the nearest whole number and you'll get the rwy number. If you have only one runway there's no need of R or L designation.
2. STARs are only assigned by ATC according to your last waypoint in the FP AND to the runway in use due to wind direction & speed AND to inbound/outbound traffic around the airport.