The Gate anime does cover the novels to a large extent. It takes the main plot elements from the novels, such as the opening of the gate to a fantasy world and the military's response. But there are some minor sub - plots and character developments in the novels that might not be fully explored in the anime due to time constraints or other reasons. Overall, if you've read the novels, you'll find the anime quite familiar, but it also has its own take on the story in some parts.
No. The Umineko anime does not cover the entire novel. There are a lot of details, plot developments, and character arcs in the novel that are either left out or not fully explored in the anime adaptation.