Please edit my entry

Or

You are never too late to take risk.

-> It is never too late to take risks [generally speaking]

-> You are never too old to take risks [speaking to another person]

Please edit my entry

Or

You are never too late to take risk.

Or: It's never too late to take risks.

No matter how old you are, you are never too old to take risks sounds more natural than the second sentence. Or you could say: It's never too late to take risks.

Please edit my entry

(I feel that your message can be brought across with this sentence: "You are never too old to take risks."

1."You are never too old" has a similar meaning to "No matter how old".

2. As you are referring to the noun "risk" in general, you pluralise it (risks).

3. "grown up" has the meaning that a person has become an adult.)

Or

You are never too late to take risk.

(Depending on what you actually mean and who your audience is, there are some options:

4. "It is never too late to take a risk." (You may be giving a piece of advise to take up a risk without appearing to be targeting someone in particular.)

5. "It is never too late to take risks." (You are referring to risks in a general sense. You may be convincing someone to be less risk-adverse.)

6. "You are never too [old] to take a risk. (You are giving a piece of advice which is targeted at someone or a group of people in particular.) 

7. "You are never too [old] to take risks." (Referring to risks in a general sense again.)