What happens when foreign characters do early Tyrian Missions?

When I did some of the Ascalonian missions with my Dervish I get warned before the mission starts? Why is this?

Its because those events that occur in the mission have already happened in the storyline, prior to your character going from Elonia/Cantha to Tyria.

It's nothing, it just tells you that those missions were already ,,done'' before your Dervish got there. You can do them, it's just a useless (IMO) thing.

If I party with other Ascalonian people in these missions will they still receive the experience reward?

Local Ascalon folks will still get the xp reward, you on the other hand wont be. Those pre lionarch missions are only good if you're going for the protector or guardian of tyria.

Alright thanks.