The elements that usually form covalent bond are 2 or more non metals.
It is not possible because in forming a Non polar Covalent bond we need equal sharing of electrons and this is made possible by bonding identical atoms.
Yes it is possible in Polar Covalent bond because Polar Covalent bond is formed by unequal sharing of electrons.
Q.4 Polar is formed by unequal sharing of electrons while Non polar is formed by sharing equal electrons.
I hope that I help you