-It is somewhat difficult for you to make a choice. If you file TN extension application and get it approved after Oct. 1, your final status will be TN, not H1. If you get it approved before Oct. 1, everything will be OK and your status will be H1 after Oct. 1. If you do not file TN extension application, you need to leave U.S. within 10 days after the TN status expires and then come back in the end of September.
2. 到10月初是否还要过境,激活H1B签证?
-No need. See above answer.