H1B (I-797A) approved but traveled on H4. Can I work directly with my I-797A and I94? or COS needed?

I got H1B (I-797A) approved in September 2015 with change of status from H4 to H1 (i.e. I got I94 along with my H1B approved). But when this petition was approved, I was in India and travelled to USA on H4 visa in November 2015.
I have below questions. Can you please clarify?

  1. Can I apply for SSN now using my approved I-797A and I94 in it? OR do I need to apply for SSN after change of status?
  2. Can I work directly with my I-797A and I94 or do I need to do change of status again?

You entered on H-4 visa and your latest I-94 is the one you received at PoE. So you cannot apply SSN at the moment and need to file COS first.

The I-94 approval was a mistake. If you were outside US at the time of approval, it should have been approved w/ consular processing and not COS.