it's very simple English !! please help me !! 急急急

你好.

本人原本是想解答你的问题的.不过细看之下,发现你的问题根本就有错,不应该是"When did he like doing when he was young? ",而是
"What did he like doing when he was young?"

因为既然你说了"when he was young",就不可以用表示时间的"when"提问.本人对纠正后的问题回答如下(其实他们都答了):

He liked both collecting stamps and listening classical music when he was young.

He liked collecting stamps and listened to classical music when he was young.

In separate sentences, as in 001.

In one sentence :-

He liked collecting stamps and listening to classical music when he was young.

He like collect stamp and listen to classical music when he was young.

Is this stence good?

He liked collecting stamps when he was young.

He liked listening to classical music when he was young.