octagon
There is no specific name for such a shape.
pentagon
An irregular polygon.
It is an undecagon
Not possible ! If the shape has four right-angles, at least two sides must be the same length.
A plane shape with these characteristics is a "hexagon".
An irregular hexagon
Either scalene triangle or a circle
A better name for "corners" would be angles, but the shape's name would be a hexagon
A parallelogram
That's an irregular quadrilateral.
A shape with seven sides is called a heptagon. In terms of its angles, a regular heptagon has internal angles of approximately 128.57 degrees each. The name derives from the Greek word "hepta," meaning seven.