The data suggests that the salt ‘X’ is Borax $\mathrm{(Na_2B_4O_7\cdot10H_2O)}$. (i) The aqueous solution of borax is basic in nature due to hydrolysis and turns red litmus blue. $\underset{(X)}{\mathrm{Na_2B_4O_7}}+\mathrm{7H_2O}$ → $\underset{\text{(Weak acid)}}{\mathrm{4H_3BO_3}}+\underset{\text{(Strong base)}}{\mathrm{2NaOH}}$ (ii) Borax swells in size upon strong heating and loses molecules of water of crystallisation to form solid (Y). $\mathrm{Na_2B_4O_7 \cdot 10H_2O}$ $\xrightarrow[-\mathrm{10H_2O}]{\text{heat}}$ $\mathrm{Na_2B_4O_7}$ $\xrightarrow[]{{\text{strong heating}}}$ $\underset{\text{Glassy (y)}}{\mathrm{2NaBO_2+B_2O_3}}$ (iii) Upon reacting with conc. $\mathrm{H_2SO_4}$, borax forms boric acid ($\mathrm{H_3BO_3}$). When crystallised from the solution, it is in the form of white crystals (Z). $\mathrm{Na_2B_4O_7+H_2SO_4+5H_2O}$ → $\underset{\text{(white crystals)(Z)}}{\mathrm{Na_2SO_4+4H_3BO_3}}$