Dear Liang Li,
As we discussed in the forum post found here: OC4-DeepCwind, the OC4-DeepCwind semi-submersible model is not currently in the public domain. So, I cannot answer your questions here. But from a quick comparison of your FAST platform input file with ours for the OC4 DeepCwind semi-submersible, there are quite a few differences.
Best regards,