What will be the formula of '$M$' nitrate based on the given Lothar Meyer curve?

The most important active step in the development of the periodic table was taken by

Whose name is not associated with the development of the Periodic Table?

Write the drawbacks in Mendeleev's periodic table that led to its modification.

State whether the following statements are true or false:
$(i)$ The first periodic table was proposed by Dobereiner.
$(ii)$ The law of octaves was proposed by Newlands in $1865$.
$(iii)$ Mendeleev was the first to propose the periodic law.
$(iv)$ Mendeleev named Eka-aluminium as Germanium and Eka-silicon as Gallium.

Explain the "Law of Triads" with examples.