How long it will take more ?

There is no expedite of the security check and the employer will have to follow their regulations regarding payroll. Contact a US immigration...

No. If you have a green card, then you don't need a new EAD at all. Contact a US immigration attorney.

Contact a US immigration attorney to review risks of immediate job change rather than waiting 6 months.

What paperwork (& when) is needed to add a spouse as a beneficiary to an i-485 application whose PD just got current?

Contact your US immigration attorney for assistance with filing for her and review the instructions at www.uscis.gov.

I got married within 90 days of my K1 but my wife does not want to put the status adjustment

Contact a US immigration attorney and perhaps a counselor to review options. The US citizen must sign the documents.

I applied for N-600 to get my certificate of citizenship, Can I also applied at Department of State to get a US Passport?

Yes, you can apply for both. Review the instructions at www.uscis.gov.

How a Canadian citizen can get green card or work permit to work in USA?

Contact a US immigration attorney to review his employment and family-based options and your naturalization options.

Review the priority date on the visa bulletin for your category and country at www.state.gov. Contact a US immigration attorney.

If i depart US on B1 visa , am I able to re enter the country with the same visa after taking f1 visa ?

Contact a US immigration attorney to review what type of rotation and the risks at re-entry.

Will I be able to apply for out of cap h1b in 2019?

Based on your facts, it appears that you are not subject to the cap. Your employer's US immigration attorney will do the review prior to filing.