Do dental sealants change if you grind?

Yes, they will wear. Dental sealants are softer than tooth enamel so if you grind your teeth, the top of the sealant will wear away. However, the sealant will stay in the depths of the pits and fissures of the tooth.
Yes. The grinding action of your teeth will wear away sealants and they may need to be replaced.
Usually no. . The sealants are in the grooves of the teeth. If someone grinds their teeth they are usually not grinding the grooves of the teeth. If they are grinding the tooth that much, some sort of dental treatment is needed.