Hi Song! Thanks for the question. This is a little bit confusing in English, but in my opinion, there is not a big difference between the two types of adjectives (east or eastern). The small difference is the feeling between the two. If I say "I live in east Spain" I am describing a region of the country. If I say, "I live in eastern Spain" I am describing the general idea but maybe not the specific region. I can say just "I live in the east". This is because "east, west, north, south" usually describe the direction or region and "eastern, western, northern, southern" can describe places but also other things such as "southern food" or "northern accent". In all of your examples, both would work fine. I hope that answers your question, but if you want to create more examples for me to look at or book a trial lesson with me to discuss grammar futher, I will be happy to help! - Teacher Alicia