1. Is the labor contract signed between the company and Liu valid? A: Invalid, illegal, legal and equal. It was discovered that his diploma was a forgery.

2. The labor contract signed by Liu is invalid. Should the company pay Liu for the labor he has already paid? A: The company should pay Liu labor remuneration, which is stipulated in the Contract Law.

3. Does the company need to notify Liu in advance to terminate the labor contract with Liu? After the probation period expires, a written notice of termination of the contract may be issued. It's stipulated in the contract law.