Short answers, pulled from the story.
The earliest Buddhist texts from India introduced divine beings known as devas, asuras, and yakshas. These figures were not creators of the universe but radiant entities existing within a cycle of rebirth called samsara.
Theravada tradition recognizes Sakyamuni as the only Buddha of the current era though Pali literature lists twenty-eight predecessors. Mahayana traditions venerate numerous Buddhas including Maitreya and Amitābha who preside over pure lands accessible after death.
The Four Heavenly Kings guard the four directions of the Sahā world and lead classes of non-human beings. Dhritarashtra rules the East while Virudhaka governs the South and Virupaksha protects the West and Vasrava guards the North.
Devas exist within one of five realms of rebirth known as gati inside the cycle of samsara and their name derives from a Sanskrit root meaning to shine linking them etymologically to divinity. Rebirth as a deva results from virtuous deeds performed in previous lifetimes but remains impermanent unlike eternal heavens these celestial realms remain bound by cyclic existence and eventual suffering.
A yidam functions as a personal meditation deity used in tantric rituals to achieve enlightenment and the term describes a state of being indestructibly bonded with the liberated nature of mind. Manifestations include Sambhogakaya Buddhas Dakinis bodhisattvas and Dharma protectors.