What parts of Asia did the mongols fail to control and why?

The Mongols fail to control very few parts of Asia such as: India, Taiwan and Japan

Explanation:

India was a territory that is protected by the Himalayas in the North so at that time was practically impossible to go across this mountain chain and conquer this territory.

The warfare of Mongols was based in the use of the cavalry then expanding to islands was impossible as well. that's why territories as Japan or Taiwan were not part of the Mongol empire.