Unknown in case there is nothing in it. Describe superficial knowledge.
Just in case: unexpected changes. Just in case something goes wrong.
Ten thousand people in Qian Qian said the same thing. Metaphor is unanimous.
There is a great possibility of dying all one's life, but little hope of living. Metaphor risks one's life.
Nothing is wrong: mistakes. It means I'm pretty sure it won't go wrong.
United as one, thousands of people are United as one. Describe unity.
The word "ten thousand mouths" is a metaphor for agreement. Same as "one word per 10,000 people".
Ten thousand people in Qian Qian said the same thing. Metaphor is unanimous.
It takes a long time to get such an opportunity. Describe the opportunity as rare.
Throwing millions means spending money carelessly, and a flower is a lot.
Hang a leak and hang a million: hook, here refers to, lift; Leak: omission. The description is incomplete, leaving out a lot.
Grasp everything with one hand: grasp. Describe that grasping the key can control the overall situation.
From a little knowledge to inferring many other things.
If you know ten thousand, you will understand the essence, and anything will do.