Which compound is not a monobasic acid?

Which of the following statements about $H_3BO_3$ is not correct?

Excess $NaOH$ can dissolve

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.

Give important trends and anomalous properties of boron.

$Na_2B_4O_7 \cdot 10H_2O \xrightarrow{\Delta} 2NaBO_2 + B_2O_3 (A) + 10H_2O$. $(A) + MnO \xrightarrow{\Delta} Mn(BO_2)_2 (B)$. $(A)$ and $(B)$ are