Short answers, pulled from the story.
Chandragupta established the Maurya Empire in 321 BCE after leading a revolt against Greek governors in India. He organized an army from the people of the Punjab region to take the throne following Alexander the Great's death.
Seleucus transferred easternmost satrapies including Gandhara, Parapamisadae, and parts of Gedrosia to Chandragupta in 303-302 BCE. This dynastic marriage alliance occurred after Seleucus was defeated crossing the Indus River with his army.
Pataliputra was surrounded by a wooden wall pierced by 64 gates and 570 towers according to Megasthenes' eyewitness account. The palace featured gilded pillars adorned with golden vines and silver birds within an extensive park.
Ashoka began feeling remorse when he personally witnessed the devastation of the Kalinga War in 261 BCE where an estimated 100,000 soldiers and civilians were killed. Following this event, he embraced Buddhism and sent missionaries to spread its teachings across Asia.
The edicts precisely name Amtiyoko (Antiochus II Theos), Tulamaya (Ptolemy II), Amtikini (Antigonos II), Maka (Magas) and Alikasudaro (Alexander II of Epirus). These inscriptions locate their territory roughly 4,000 miles away from India.
The Maurya Empire ended in 180 BCE when general Pushyamitra Shunga killed Brihadratha Maurya during a military parade without any heir. This event gave rise to the Shunga Empire and left the Khyber Pass unguarded triggering foreign invasions.