They are called congruent angles.
Acute angles
rectangle.
4 right angles, by definition, are four angles of the same measure, and therefore must be congruent angles.
Equaliteral Triangle
Equilateral
A contraction
Yes. Eg. Square, Rectangle. Yes, and there is a special name for such a quadrilateral. It is called a rectangle. If all four sides are equal in length as well as having four right angles, then it is called a square.
octagon
It does not have a specific name. I think that, of the named quadrilaterals, only a trapezium can have four different angles.
regular polygons
There is no particular name.
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