Yes, he also taught about karma and the cycles of life. He just suddenly felt he had all the answers. No one taught him anything. So, it all happened in his mind. You could say he suddenly became wise. Thats all.
Hey, dun know means dun know. No need to smoke. This is not an examination.
The Buddha, as a Bodhisattva and a normal sentient being before that, had gone through countless lives practising and figuring out the Truth. His practice came to fruition 2500 years ago under the Bodhi Tree when he meditated to gain Enlightenment.
This Enlightenment is not "sudden" or "just happens". It is the result of eons of practice. As for who taught him, the first beginning, where is the Buddha now? The Buddha taught that it is not fruitful to know all this as it is beyond our understanding.
I know this seems like a copout but consider this. What is the first number and what is the last number? You can deduce that there is no first number and there is no last number? Thus there is no beginning or end to samsara.