Do dental sealants prevent gum erosion?

No. No. Sealants are put onto the biting surface of the teeth... Not near the gums.
No. Dental sealants are to seal the grinding surface of the molars and premolars to help prevent cavities.
Not Really. Dental sealant will typically not prevent gum erosion.
No. Dental sealants protect the grooves of the back teeth. They have nothing to do with protecting the gums.