Intercession of the Theotokos is celebrated in the Orthodox Church on October 1. The Greek Church moved it to October 28 though. It is celebrated universally in the Orthodox Church however in the Eastern slavic countries it's considered one of the biggest feasts after Easter and 12 major feasts while in Greece it's of lesser importance. I cannot really speak for Balkan countries or Arabs.
The origin of this feast is the apparition of Theotokos in Constantinople while it was being seiged. It's only not clear what siege was that exactly. The most common date believed is 910.
And that icons indeed looks like it was painted in the Eastern Catholic circle. I cannot decipher it since the letters are to small.