The stability of $+1$ oxidation state among $Al$,$Ga$,$In$ and $Tl$ increases in the sequence:

The correct statement$(s)$ for orthoboric acid $(H_3BO_3)$ is/are:
$(A)$ It behaves as a weak acid in water due to self-ionization.
$(B)$ Acidity of its aqueous solution increases upon addition of ethylene glycol.
$(C)$ It has a three-dimensional structure due to hydrogen bonding.
$(D)$ It is a weak electrolyte in water.

Which reactions can be used to prepare diborane?
$I.$ $3NaBH_4 + 4BF_3 \xrightarrow{\text{ether}} 2B_2H_6 + 3NaBF_4$
$II.$ $2NaBH_4 + I_2 \to B_2H_6 + 2NaI + H_2$
$III.$ $2BF_3 + 6NaH \xrightarrow{450 \ K} B_2H_6 + 6NaF$

When orthoboric acid $(H_3BO_3)$ is subjected to strong heating,the residue left is

Is boric acid a protic acid? Explain.

Which of the following show diagonal relationship?