yes
Yes.
No
An [equilateral] triangle, square and hexagon are the only regular polygons which, by themselves, will tile a surface.
Yes.
yes
Yes a triangle will tessellate leaving no gaps or overlaps
Yes.
Yes.
yes it does
No.
No
heptagon and an equilateral triangle
An [equilateral] triangle, square and hexagon are the only regular polygons which, by themselves, will tile a surface.
Yes.
It can, by itself.
Yes all triangles tile because their angle sum, 180 degrees, is a multiple of 360 degrees.