Does a woman sin if she uncovers her face while wearing full Islamic attire and not beautifying herself or causing any temptation, despite the existence of a jurisprudential disagreement on this issue?

Regarding the obligation of a woman covering her face from non-mahram men, there is a difference of opinion. The majority view is that it is not obligatory. Therefore, whoever does not believe in its obligation incurs no sin by uncovering it. However, it is better to cover it completely for the sake of protection and modesty, and to emulate the Mothers of the Believers.