How does the backbone protect nucleic acid from hydrolysis?

By preventing bases from being damaged present in phosphate sugar backbone.

Explanation:

The sugar phosphate backbone is a significant structural component of DNA. It comprises of 5-carbon deoxyribose sugars and phosphate gatherings. DNA is twisted into a right-gave twofold helix. The strands are anti parallel for example one runs 3' to 5', the other run 5' to 3'.

This is finished by the sugar phosphate backbone contorting around itself in a curl or coil. The motivation behind this twisting or coiling is to ensure safety of the nitrogenous bases inside backbone, and keep them from being damaged. DNA is entirely stable because of rungs of hydrophobic "ladder" and adversely charged phosphate sugar backbone of DNA. These highlights cause DNA to can repulse water and would not hydrolyzed.