The answers are in this order:
1. Southwest Asia;
2. East Asia;
3. Southeast Asia;
4. South Asia;
5. Central Asia and Siberian Russia;
Asia is the biggest continent on the Earth, so it is no wonder that it has multiple regions, five to be more specific, all of which are relatively big on their own. Each of these regions has its own unique, characteristics, linguistically, religiously, culturally, in the physical appearance of the people... Also, each of these regions has its own unique geography, while some are dominated with arid and semi-arid landscapes like Southwest Asia, some like Southeast Asia are covered with tropical rainforest, while Easy Asia is dominated by the continental climates with monsoon influences. Some are dominated by highlands while some are dominated with mountains etc.