Why did Alexander not invade india?

Alexander did or not invade India:

Alexander conquered most parts of the Western World, but there is a great deal of controversy over his invasion of India. In BC 327 Alexander came to India, and tried to cross the Jhelum river for the invasion, but was then confronted by King Purushottama (King Porus, according to the English rendition.) According to Indian history he was stopped by Porus at his entry into the country, but most of the world still believes that Alexander won the battle. Many of Internet links claim that Porus was defeated by Alexander, then he returned to Greece, giving back the Kingdom to Porus.  

This link from wikipedia says that "After victory, Alexander made an alliance with Porus and appointed him as satrap of his own kingdom".This is difficult to believe: IMO no noble king would accept his kingdom back after being defeated.

Also claimed there: "Exhausted and frightened by the prospect of facing another giant Indian army at the Ganges River, his army mutinied at the Hyphasis (modern Beas), refusing to march further East. Alexander, after the meeting with his officer Coenus, was convinced that it was better to return." Did that mutiny actually occur?

After traveling hundreds of miles from Greece and even winning the battle, why would Alexander return without conquering India?

Specifically, I want to know what actually happened in the battle between Alexander and Porus: Who won? Was it true that King Porus defeated Alexander and made him flee back to Greece ? Whoever won the battle, Alexander or Porus, what historical evidence is there regarding what actually happened in that encounter?