I went to the park because I needed to clear my head, and when it was morning, I returned home.
In this sentence, we see two subordinate clauses and two independent clauses.
The two subordinate clauses are 'because I needed to clear my head' and 'when it was morning'. The two independent clauses are 'I went to the park' and 'I returned home'.
However, the second subordinate clause—which follows a coordinating conjunction ('and')—is fronted. Therefore, I would like to know if there is any rule that dissuades fronting immediately after a conjunction, or do we treat it like any normal sentence? (This is a broader expansion on a previous question I had.)
Here are two more examples, each of which is different.
It was true that in the morning, his head would be clear.
In the beginning, his head was cloudy, but in the end, he felt rejuvenated.