In November 2018 my last H1B extension got approved but my dependents H4 applications are still pending meanwhile we went to India and got stamping for all (including dependents). If i file extension for my dependents will it impact the approval since the old case is still pending and the I-94 number is mismatch?
No, it should NOT impact. You can send a request letter to withdraw the old ones stating the reason. Check below.