Option 1 suggests that glass can be etched by diamond and cone, sulphuric acid. This is partially true. Diamond, due to its hardness, can indeed scratch glass. However, glass is resistant to sulphuric acid, so it cannot etch glass.

Option 2 states that glass can be etched by hydrofluoric acid and aquaregia. Hydrofluoric acid is indeed used to etch glass, but aquaregia, which is a mixture of hydrochloric acid and nitric acid, does not have the same effect on glass.

Option 3 suggests that glass can be etched by diamond and hydrofluoric acid. This is true. Diamond, due to its hardness, can scratch glass, and hydrofluoric acid, unlike other acids, can etch glass.

Option 4 states that glass can be etched by hydrofluoric acid and cone, sulphuric acid. As mentioned earlier, hydrofluoric acid can etch glass, but sulphuric acid cannot.

Hence, option 3 is the correct answer.