the status "required reviews completed"
As the status message suggests, the Reviewers have completed their reports and submitted them online via the Elsevier manuscript system. Your paper is now with the Editor. Since the status did not change for the last 2 months, we can assume one of the following:
 - the Editor did not have time to deal with your manuscript yet;
 - the Reviewers Reports are contradictory, and your paper requires more attention and more time of the Editor than usual.
In my experience, the first explanation covers most of the real-life cases.

It is completely OK to write a polite message to the Editor asking them about the status of your paper. However, be prepared to receive no answer, or not-really-an-answer.

Yes, there is always a possibility that your paper can be rejected as a result of the review process. However, the Editor's decision should normally be made based on the results and the writing of the manuscript. If your communication with the Editor is polite and justified, there is no risk that it can reduce the chance of your paper to be accepted.