You cannot file for adjustment of status if you are going to be gone for 14 - 18 months, since adjustment takes less than a year. Instead, try just filing an immigrant visa petition and your mother can immigrate with the immigrant visa.
The above is intended only as general information, and does not constitute legal advice. You must speak with an attorney to discuss your individual case.
Yes. She will be able to eventually, when she is an LPR. Until then, Advance Parole it is.
The information contained in this answer is provided for informational purposes only, and should not be construed as legal advice on any subject matter,not should it be viewed as establishing an attorney client relationship of any kind.
Your mother can travel abroad with her Advance Parole while her I-485 is pending. She can apply for a re-entry permit after she receive her I-485 approval. She shouldn't plan to be out for 14-18 months at this point in her case. Schedule a consultation for your mom to discuss her options in detail.
Attorney Jennifer Ahn's answer is to provide general information only, and should not be construed as legal advice on any subject matter. The content of this answer is not intended to substitute accurate legal advice, which is relevant to all the facts and circumstances of your specific case. This answer does not create an Attorney-Client relationship. (847) 297-9200
It is possible, if your mother doesn't return in time for her interview, that her case will be considered abandoned, and she would need to start all over. If she does return and gets her green card, then afterwards she can apply for a reentry permit.
This answer does not create an attorney-client relationship and is not meant to be relied upon as legal advice.