I just got H1B status approved effective from Oct 1st. My spouse change of status from F2 to H4 is still pending. Can she stay in US after Sep 30th?

The I-129 and I-539 are separate adjudications, and in most cases today are not together adjudicated. Part of it is because I-539 applicants must be scheduled for biometrics while I-129 beneficiaries are not. Your spouse is legally allowed to remain in the US until USCIS makes an adjudication on the application. Due to the limitations of the Lawyers.com Forums, Alan Lee, Esq.'s (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.