Can instances of significant objects reside in the dynamic memory allocation area?

Yes, instances of value types (structs) in C# can reside in the managed heap. Although value types are usually stored on the stack, if they are fields of a reference type or if their instance is created using the new operator inside an object that is allocated on the heap, then these instances will be placed on the heap.

Example:

struct Point { public int X, Y; }

class Container {
    public Point p; // struct field inside a class
}

var c = new Container(); // Container object is allocated on the heap
// The value type Point inside Container will also be on the heap

Thus, the placement of a value type instance depends on the context, not just on the type itself.