Here’s a rewritten version of the sentences:

1. "I suggested to Tom that he finish his test within the allowed time."
2. "The exam wasn't as difficult as we had thought."
3. "If Yumiko doesn't seek advice from her counselor, it won't help her."
4. "I have known my English name since we met in 2012."
5. "Tom has never considered how I feel."
6. "Teenagers expressed their feelings in the past."
7. "No river in the world is as deep as the Naire."
8. "Many people believe that the Japanese eat with their eyes."
9. "I apologize for not having the skills to assist you with your math homework."
10. "I wish I could swim as well as Stan."
11. "The cream is quite thick; it is ready to use."
12. "The cream is extremely thick."
13. "I have never read such an interesting novel as Tom Cam."