no
a decogon
8
If decogon were a real word then the prefix would, could be de-, dec- or deco-. But it is not a real word and so there is no prefix.
12
it is a ten sided and ten angled figure
A decagon has 10 sides
Decogon * * * * * A decagon, actually.
No cones can not tessellate.
Yes * * * * * No. A star will not tessellate.
A square will tessellate leaving no gaps or overlaps but a circle does not tessellate.
it is a ten sided and ten angled figure
No, it can't be tessellate.