There are decagons which will tessellate.
No.
There are decagons which will tessellate.
There are decagonal shapes which will tessellate the plane.
No. No shape with 7 or more sides will tessellate with multiple copies of itself. All traigles and quadrilaterals will tessellate, there are 14 irregular pentagons (the last was discovered in 2016), and a number of hexagons - including the regular hexagon.
Yes. For example if you have a decagon in which the top, bottom and the four sides on the left are as in a regular decagon, and if the four sides on the right make the shape concave. These decagons will "slot" into one another.
yes of course * * * * * A decagon does NOT tessellate. All triangles and quadrilaterals do, there are 14 tessellating pentagons and a number of hexagons (including regular hexagons). There are no tessellations which use polygons of the same shape - regular or irregular - for polygons with 7 or more sides.
No cones can not tessellate.
A square can tessellate but a regular pentagon can't tessellate
A square will tessellate leaving no gaps or overlaps but a circle does not tessellate.
Yes * * * * * No. A star will not tessellate.