Which sentence is correctly punctuated?

I can't say that either one is wrong, although i'd probably write the first sentence. I would omit the last comma.

Regarding the first version, Tang, I can't agree with Set. I'd omit the second comma and maybe the first also

However if you omit the third you introduce a subtle ambiguity: He could have somehow been driving several cars but he lost control of only one, identified by the fact that, unlike the others, at some time previously it has crashed into a tree

I'd agree tho it's a stretch

Second version not collo

They are both wrongly worded sentences but the first sentence is worded correctly and also correctly punctuated if you lose the second "he".

Or:
He was speeding, lost control of his car, and crashed into a tree.

This all sounds a bit Star Trek.

Though it hardly the norm, the 2nd one could represent someone emphasizing 'and'.

He was speeding annnnd, as a result, he lost control of his car, which crashed into a tree.

Punctuation is not so much a matter of correct as it is a matter of style, Ms Tan.

There are many style manuals put out by many different organizations. Many are house manuals for particular publishing groups and there is a degree of difference among them.

That's one of the reasons you get so many different opinions from so many native speakers. And in this respect they are all quite competent. One of the reasons you can/could get so many different opinions is that each individual could be viewing the intent of the speaker/writer differently.