Which of the following is used to avoid leakage of electrolyte in a dry cell?

$Zn_{(s)} | Zn^{2+}_{(aq)} || Cu^{2+}_{(aq)} | Cu_{(s)}$ is

Which among the following is an example of a metal-metal ion electrode?

What happens to the oxidation number of $Mn$ during the operation of a dry cell?

If less than $1.1 \ V$ external opposite current is passed through the Daniell cell,for such condition answer the following questions :
$(1)$ Give reaction of cathode,anode and redox.
$(2)$ Between $Zn$ and $Cu$ which metal dissolve in solution ?

Write a note on mercury cell $(Zn-Hg)$.