It is a tetrahedron pyramid that has 4 faces, 6 edges and 4 vertices.
a "regular" one
A regular polygon is a polygon with congruent sides and interior angles.
It is an equilateral polygon. It is not a regular polygon. For the polygon to be regular, it is not enough for the sides to be congruent: all the angles need to be congruent as well.
No. You also need all of the sides to be congruent. For example, a rectangle has four congruent angles, but it is not a regular polygon.
A polygon with all sides congruent is a square.
A regular polygon
That is called a regular polygon.
It is a regular polygon
a regular polygon
The answer is in your question it is defined to be a regular polygon as for example an equilateral triangle
Regular polygons have congruent sides and angles
It is a regular polygon