How to merge two objects in inkscape?

Question

inkscape

How to merge two objects if one is inside the other.
Here's the first one

Here's the second

one And here's what happens if you combine with the help of union

It is necessary that after the union the picture does not change, but in the end you get one solid contour.

Answer 1

Your second object is a rectangle, so everything is correct in the result. To have a frame, first convert the outline of the second object to curves through the menu: Path -> Outline Stroke. And then combine.