1. Are sp^​3d⁴ and sp³d⁵ hybridizations possible? Why/Why not?

2. What shapes would sd (or sd²) hybridizations take?

a. This type of hybridisation is possible. Ex TaF₈^3- is square antiprismatic shape and type of hybridisation is sp^​3d⁴ 
[ReH9]^2-  is tricapped trigonal prismatic shape and type of hybridisation is sp^​3d⁵ ​

b. The shapes of sd hybridisation gives polyhedral coordinate geometry.