Early life of the Buddha's references Many accounts of the Buddha's life describe Śuddhodana preventing his son from leaving the palace to avoid a prophecy said by Asita. For example, this site says:


  Suddhodana was determined to see his son become a king so he prevented him from leaving the palace grounds. But at age 29, despite his father's efforts, Siddhartha ventured beyond the palace several times.


In what sutta (of any canon or tradition) the Asita prophecy and the above events are described? The only sutta I know about Asita is Snp 3.11 but it does not mention the alternative prophecy for his future, and most suttas I know have the Buddha describing the palaces he lived in, but not his father's plans to prevent him from becoming a Buddha.

Also, it's commonly said that, after going outside the palace, he saw a sick, an old, and a dead person. Is this in the pali canon? DN 14 says Vipassi was the one who encountered these people. I only know of suttas such as AN 3.39 where it says that the Bodisatta reflected on sickness, old age and death. Do these stories got conflated?
In what sutta (of any canon or tradition) the Asita prophecy and the above events are described?  ...
  


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  Asita apparently see the child Bodhisattva either on the very day that he was born, or within
  three days thereafter. The Buddha,vaṁsa Commentary mentions the 5th day as the “head lustration” and
  naming day, when 108 brahmins were invited. If these, 8 of them—beginning with Rāma
  (J 1:56, v270)
  —were versed in reading the 32 marks of the great man. Seven of them raised two fingers, predicting that
  the child would become a wheel-turner if he lived a household life, and become buddha if he renounced
  the world.
  
  The youngest of them, Koṇḍañña, was certain of the child’s future, and raised one finger, proclaiming
  the he would surely become the Buddha. Koṇḍañña later becomes the eldest of the group of 5 monks who
  attended to the Bodhisattva before his awakening. However, Asita is not mentioned amongst these brahmins.


Source: Introduction to Nālaka Sutta by Piya Tan




  
    ...  he saw a sick, an old, and a dead person. ...
  
  
  Even though I was endowed with such fortune, such total refinement, the thought occurred to me: 'When an untaught, run-of-the-mill person, himself subject to aging, not beyond aging, sees another who is aged, he is horrified, humiliated, &amp; disgusted, oblivious to himself that he too is subject to aging, not beyond aging. If I — who am subject to aging, not beyond aging — were to be horrified, humiliated, &amp; disgusted on seeing another person who is aged, that would not be fitting for me.' As I noticed this, the [typical] young person's intoxication with youth entirely dropped away.


Source: Sukhamala Sutta, Four sights


  And what is ignoble search? There is the case where a person, being subject himself to birth, seeks [happiness in] what is likewise subject to birth. Being subject himself to aging... illness... death... sorrow... defilement, he seeks [happiness in] what is likewise subject to illness... death... sorrow... defilement.


Source: Ariyapariyesana Sutta, Four sights