Based on the hints provided, the word you are looking for seems to be "key." Here's how it fits:

1. First word hint: "This word is used in common for all meanings."

   • The word "key" is used in various contexts, such as a key to a lock, a key in music, a key in a database, or a key point in an argument.

2. Second hint: "Shall we demonstrate great reasoning skills like a detective?"

   • A detective often looks for a "key" piece of evidence or a "key" clue to solve a case.

3. Meaning hints:

   • If it's difficult, I'll give you a second hint.
   • If it's still difficult, I'll explain the meaning of the word.
   • The word in the OO part is the correct answer.
   • OO is included in the meaning of all words.

The word "key" fits perfectly because:

• It is a common word used across multiple meanings.
• It relates to detective work as a "key" clue.
• "Key" is included in the meaning of all the hints provided, as it is central to understanding or unlocking the puzzle.

So, the answer to the quiz is "key."