Game of Thrones raiding

By Deadscrote, in A Game of Thrones: The Board Game - A Dance with Dragons

Can a raid order placed on land remove a support order placed in a sea zone?

No.

Rulebook, Page 14:

A Raid Order placed on a land area can never raid an adjacent
sea area.

Next question... can units in an area with a support order support multiple adjacent areas on the same turn or are they limited to supporting just one adjacent area per turn?

Rulebook, Page 18:

When a player grants support, his Support Order token is not removed after the combat. A Support Order may support any number of adjacent combats in the same game round.