Is it permissible for the husband to benefit from his wife’s gold, which he gifted to her upon marriage, knowing that it is documented as her right and he promised to return it, and does the wife have the right to prevent him from doing so?

The gold given by the husband to his wife, whether as a gift or as part of the dowry, becomes the property of the wife. The husband has no right to dispose of it, and the wife has the right to prevent him from using it, even as a loan or for temporary use, unless she voluntarily consents to it.