What is the ruling on a group of pilgrims praying Dhuhr and Asr shortened (qasran) but not combined (dun jam'in) on the Day of Arafat, and what is the ruling on another group praying combined and shortened (jam'an wa qasran), and is their Hajj valid, and what are the implications thereof?

Combining and shortening the Dhuhr and Asr prayers in Arafat is a confirmed Sunnah. Whoever does not combine them has gone against the Sunnah, but their prayer is valid and there is nothing upon them. As for a group searching for an Imam to combine the two prayers, this is not considered an act of leaving the congregation; rather, it is a pursuit of what is better. The Hajj of both groups is valid.