Well, it's not a straightforward yes. Some DC movies are direct adaptations of comic stories, but others take elements from multiple comics or even deviate significantly to offer a fresh take on the DC universe.
Not all DC Comics novels are suitable for all ages. Some, like 'The Dark Knight Returns', have a darker and more violent tone that might not be appropriate for very young readers. However, there are also many that are family - friendly, like some of the Superman stories.
Most DC Comics novels are suitable for a wide range of ages. However, some of the darker and more complex ones, like 'The Dark Knight Returns' or 'Arkham Asylum: A Serious House on Serious Earth', might be a bit intense for very young readers. But in general, there are many that are family - friendly and can be enjoyed by kids as well as adults.
The list of all DC Comics is huge. It encompasses various series and standalone issues featuring heroes, villains, and teams. For instance, there are comics for Justice League, Green Lantern, and Aquaman, among many others. The number and variety are almost limitless.
The DC Universe doesn't encompass every single comic. It features a significant amount, but there are many that are not included for various reasons like licensing and availability.