I want to change visa status from H1B to H4 but my project was ended on Jan 1st, 2017. I don't have paystubs since Jan 2017.

As my collegue mentioned you can try but likely not approved. Consider departing US and return with H-4 visa. Canada is possible but has issues.

Can a sibling apply for college degree during or when sibling application for green card is pending

Yes it is possible. One issue among others will be convincing Immigration authorities of non immigrant intent

Multiple VISAs files and pending

No conflict you should know if selected within 4 to 6 weeks

My wife is an American citizen- I over stayed my visa( 1 1/2 year) I am back in France now How can i go back LEGALY to stay ?

With overstay of 1.5 years you need a waiver of 10 year bar in addition to visa petition approval. immigration attorney assistance is recommended

Social security number information change after divorce( no last name change)

Change is okay or be prepared to provide explanation to CIS

Petitioning my step daughter...

Not to file the petition, however, very likely ta release will be required before the child's government will permit migration.

What amount goes in form i864 part 6 lines 13a-c for aomebody that is self employed and has received a 1099?

Follow the directions carefully when completing on your own. Specific advice if needed is best directly from your immigration attorney as a review...

Why Uscis is not closing my case?

Possibly not a priority for USCIS or it remains an active matter

Yes you may file for adjustment while 730 is pending

Can i stay in usa legally while my h1b petition is pending?

You may remain in US While decision is pending if filed with USCIS before status expires.