Does TM need to be registered?

Answer 1

Assuming you mean "does it need to be registered to be enforceable", the answer is "not necessarily."

In the United States, for example, the first use of a distinctive mark in association with goods or services may create statutory and common-law priority rights that can be used to prevent others from later using a mark that is "confusingly similar."

However, registration (state or federal, or both) provides additional protection and makes the enforcement of a valuable brand that much easier.