Why Allah Didn't Send Al-Quran to Adam AS

We were born as a baby. Then we reached age of child. At the age of 4-6. We were learning at kindergarten. Ensuing that, we will go to primary school from the age of 7 until 12. Then, we go to secondary school. After we finish our school. We will go to college or any university. 

Okay why in the age of 4 we didn't straightly go to university? Yeah because we didn't reach the level to go straightly. We need a step by step. So does Quran. Allah revealed it step by step. Because every generation, Allah will change-up the syariah, the law. Because arak or champagne or any other alcoholic drink was not forbidden, was not haram once upon a time. We can speak in the salah once upon a time. So, that is the reason why Allah didn't send Quran to Adam AS. But He sent to His last Messenger Muhammad SAW. 

If there any mistakes. Please correct me. May Allah forgive me