Use of past perfect tense

Question

We normally use past simple tense to talk about the past and past perfect tense to talk about the past in the past, i.e. to talk about some event that that happened before some other event. I often see that when we use past perfect tense, we use it with past simple tense,e.g. I had learned Chinese before I moved to China. What if I use a non-finite adverb clause, e.g. I had learned Chinese before moving to China? How different are these two alternatives?

Answer 1

I had learned Chinese before I moved to China.

I had learned Chinese before moving to China.

There is no difference in meaning of these sentences except that the latter is more formal.

Answer 2

No difference in meaning - finite verb or gerund

The past perfect tense is used to describe a past event that occurred prior to another past event.

1. Simple past tense can be used if 'before' is there in the sentence.

I often see that when we use past perfect tense, we use it with past simple tense,

If you rewrite the sentence as -

I learned Chinese when I moved to China. It is unclear from this sentence which activity occurred first. (learned Chinese before or after).

The order of events is indicated by using the past perfect tense. Thus, in order to communicate the idea, the past perfect is needed here. Your original sentence can be rewritten without changing the meaning -

I had learned Chinese when I moved to China.

When you use before or after in a sentence the meaning can be conveyed by using the simple past tense.

I learned Chinese before I moved to China.

2. What if I use a non-finite adverb clause, e.g. I had learned Chinese before moving to China? How different are these two alternatives?

There is no difference between the two. But 'moving to China' is an adverb phrase and 'moving' is a gerund.

Ref : https://study.com/academy/lesson/gerunds-verbs-that-end-in-ing.html#:~:text=A%20gerund%20may%20function%20as%20an%20object%20of%20a%20preposition,noun%20and%20ending%20in%20%2Ding.