What you initially stated is true. One cannot possibly attain the Arahantohhod in just one lifetime.
– However, the rebirth process is so long that each and every living being existing now MUST have started on following Buddha Dhamma long ago.
– The Buddha said each living being’s existence can be traced backward for many, many eons, and he could not see a “beginning.” It extends to an infinite amount of time back.
– See, “Sansaric Time Scale, Buddhist Cosmology, and the Big Bang Theory”
Therefore, the following in your statement is NOT correct: “If the above underlined statement is true, then Angulimala must have started on the path long ago before this lifetime, so that he at least are in Sotapanna stage when born as Angulimala.”
Angulimala most definitely followed the Path in previous lives.
– However, if he had attained the Sotapanna stage in a previous life, he would not be capable of killing 999 people.
The important thing to realize is that we all must have done both good and bad deeds in previous lives.
– We are born now due to the results of a good kamma.
– One COULD be born in an apaya when a bad kamma re-surfaces unless one attains at least the Sotapanna Anugami stage.
– That is what is meant by “one is not released from the apayas until one attains at least the Sotapanna Anugami stage.