I would like to clarify some of the confusion. DNA and RNA are very similar, apart from the backbone sugar (RNA has an extra hydroxyl group) and One of the bases, thymidine in DNA, is replaced by Uracil.
The hydroxyl group makes it more liable to acid-base hydrolysis
In fact, both DNA and RNA can form double helices, and other superstructures, such as hairpins, quadruplexes; triplexes ...
A lot is still not well understood, but RNA actually plays a huge role in cells and is much more than just a messenger between DNA and proteins ...