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Can I say,

The tortoise crawled slowly and steadily passed by the hare.

The tortoise crawled slowly and steadily. He passed by the hare.
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Vincent TeoCan I say,

The tortoise crawled slowly and steadily, passing [by] the hare.

The tortoise crawled slowly and steadily. He passed by the hare.

Also, Crawling slowly and steadily, the tortoise passed the hare.
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Thanks. But, lots of my friends would say , " walked slowly passed by the tree / the boy...."

Isn't incorrect?
It is incorrect; a native English-speaker would normally say:

"walked slowly passed by past the tree / the boy.."