It appears this would be Canada based on information provided.

More information is needed to provide a meaningful response.

Yes you may petition for the I130 while your mother has a visitor visa.

You will need separate I864 for each applicant.

No this shouldn’t impact future immigration prospects.

Yes if you have a valid visitor visa.

No this shouldn’t be a problem at all.

No not after you have been approved for your GC.

Write to the service center that is processing your case.

Are you rescheduling or withdrawing? Contact USCIS with request before interview.