what is a shape that have 8 sides
Yes
There is no specific name for such a shape.
It is any two-dimensional shape that has 4 sides formed by straight lines. It can be a square, rectangle, rhombus, rhomboid, parallelogram, or trapezoid. Its four included angles will total 360° (for a concave shape, one will exceed 180°).
That's impossible. A shape has three or more sides/faces. There is NO shape that has one or two sides/faces
trapezium
There is no specific name for such a shape.
A two-dimensional shape with one curved side and four straight sides can be created, but there is not specific name for such a shape.
Two straight lines connected by one curve is the basic horse-shoe shape.
Yes
A shape with at least one side that is not straight, a shape where a pair of straight lines cross one another (like an angular figure of 8).
There is no specific name for such a shape.
A rhombus is one of them
a right triangle
Any shape with four straight sides is a quadrilateral. A trapezoid has one pair of parallel sides, and a parallelogram has two pairs of parallel sides. So any shape with four straight sides and no parallel sides is a quadrilateral that is not a parallelogram or trapezoid.
It is one plane shape consisting of four straight sides (and four vertices).
It could be a cylinder
You do not mention the number of sides or even if the sides are straight, but you are probably asking about a trapezium or trapezoid.