First, your wife's H4 application will be deemed abandoned if she travels out US on Feb while the application is still pending. But it's still fine, she is still legally staying after H4 COS submission till she leaves US.
She can certainly come back with H4 visa (go to consulate), or wait till her H1 application approved and use H1 for entry (till OCt 2008).
Here are p-2-p answers to your questions:
(1) If the attorney filed her H1B visa on April 1st from USA and we are still in China at that time, if the H1B visa is still pending, can my wife apply for H4 visa to come back to USA?? Will this affect her H1B visa approval??
Not affect H1 approval but she does not have valid H1 visa stamp. She has to go outside again to get a visa stamp for H1 in order to work.
(2) Differnt from above, if her H1B visa has been approved, can she apply for H4 visa to come back to USA and use H1B visa from Oct. 1st, 2008?? Will H4 visa from China supercede the H1B approval since it is approved after the H1B approval??
Same thing, She can enter with H4 and stay with H4 then again go out of US with H1 approval notice to activate her H1.
Best advice is to enter US with H4 before Apr 1. Then company will file H1b petition on Apr 1. She will receive H1 approval notice with I-94 same as H4. She does not have to leave US to get a stamp.
Hope this helps.
