If I have a hextech chest available to earn and someone in my premade gets an S and gets me the chest can I not earn another chest on the champion IM playing or the champion my friend is playing? and do both of you need to be playing a champ you haven't earned a chest on?
You'll get the chest for the champion you are playing only, meaning you can't have earned one yet this season on that champion in any way. It also doesn't matter if your premade ally that gets an S has any chests available, their predicament doesn't affect whether you get one or not.
Read more about Hextech Crafting & Mastery here; http://boards.eune.leagueoflegends.com/en/c/champions-gameplay-en/KZnWzcGK-hextech-crafting-and-mastery-frequently-asked-questions
