An equilangular polygon is a polygon who's angles are equal.
A polygon can be equilateral but not always equiangular. Some examples of this are rhomboids and other polygons like pentagons and hexagons.
Not normally
All regular polygons.
No because it has 2 equal interior acute angles and 2 equal interior obtuse angles but its 4 sides are equal in length
An equilateral triangle and a square.
60 degrees.
Equilateral and Equiangular triangle
If by equilangular you mean all angles are the same, then no - the sum of the angles of a triangle must be 180o, so if all 3 are the same they must each be 60o and the triangle is called equilateral. However, an obtuse isosceles triangle is possible as the equal angles are the other two angles to the obtuse angle.
They can be any figure
No because a parallelogram is a quadrilateral that has 4 sides but any triangle has only 3 sides.
The figure which is always a rectangle is a SQUARE having four straight sides and four right angles.