I came here in July 2007 on Business Visa for 94 days, then again come back on L1-B Visa In November 2007. For calculating substantial presence test for 2008 can I include my Business Visa days as well?

If I ask for extension for filing tax returns, then can I file tax return as resident alien for 2007?

Yes, you CAN count the business visa time.

Yes, if you are married.

If single, then you should file as a non-resident alien.