Identify the hybridisation and geometry of $SF_4$ molecule respectively.

The hybridization of the central atom will change when

Predict the hybridization of each carbon in the molecule of the organic compound given below. Also,indicate the total number of sigma $(\sigma)$ and pi $(\pi)$ bonds in this molecule.
$HC \equiv C-CO-CH_2-COOH$

Explain the bond formation by $sp$ orbitals.

If the dipole moment of an $MX_3$ molecule is zero,which orbital is used by the $M$ atom to form sigma bonds? (Atomic number of $M < 21$)

Choose the correct code of characteristics for the given order of hybrid orbitals of the same atom,$sp < sp^2 < sp^3$:
$(i)$ Electronegativity
$(ii)$ Bond angle between same hybrid orbitals
$(iii)$ Size
$(iv)$ Energy level