I have come to these conclusion after reading all these discussions.
Correct me if I am wrong, and please add more if you have.

> If you apply for TPS then only way you should travel outside of US is using Advance Parole (AP).

> Once your TPS gets approved, and you travel outside of US without AP, your TPS will be terminated.

> You can apply for TPS now, and apply TPS EAD whenever you want until the TPS expires.

> If you already have EAD, and you apply TPS EAD, your previous EAD will be terminated.

> To apply for your Travel Document (AP), first TPS needs to be approved.

> Once you leave US, it is not 100% guarantee to get back to US, regarding the VISA/Status you have. So always have enough documents.

> After your TPS gets approved, your status will be TPS, regardless of the status you have.

I have one question: After USCIS started processing the case, what is the status now. One of my friend came to US as tourist, and his I-94 date will expires in 20 days. It will take 3-4 months to approve his TPS, and by that time he will be out of status. So what is the best things to do?

Thanks in advance.