Reg H4 dependent Visa clarification


I m holding H1B Visa valid UpTo Oct 2017. Now I am going to process amendment and extension same time. In mean time I have to raise a dependent Visa for my spouse. Please let me know whether I can raise dependent Visa once it got receipt number for amendment and extension. Or I have to wait until my petition gets approved.

How long it will take to get receipt number for amendment and extension process?
If I can raise a dependent Visa with receipt number how long my spouse’s visa validity will be?