Michael Jackson was 11 in Diana! when he played the character 'Self'.
That was over 53 years ago in 1971.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
In 2009 he died aged just 50, starring in 123 films in his career, 118 of those after Diana! was first released. If he were alive today he would be 65.
In Diana!, I think Michael Jackson looks: