In a molecule of pyrophosphoric acid $(H_4P_2O_7)$,the number of $P-OH$,$P=O$ and $P-O-P$ bonds/moiety(ies) respectively are:

The crystalline form of borax has
$(A)$ tetranuclear $\left[B_4O_5(OH)_4\right]^{2-}$ unit
$(B)$ all boron atoms in the same plane
$(C)$ equal number of $sp^2$ and $sp^3$ hybridized boron atoms
$(D)$ one terminal hydroxide per boron atom

Identify the correct statements from the following:
$(i)$ The atomic radius of $Al$ is lower than the atomic radius of $Ga$.
$(ii)$ Boron exists in many allotropic forms.
$(iii)$ The melting point of $Ga$ is lowest among the group $13$ elements.

Which of the following orders is not correct against the given property?

$H_3BO_3$ is

For the following halides: $(1) \ BCl_3$,$(2) \ AlCl_3$,$(3) \ GaCl_3$,$(4) \ InCl_3$,what is the decreasing order of their Lewis acid strength?