Which of the following compounds will give a yellow precipitate with iodine and alkali?

Consider the reaction :
RCHO + NH₂NH₂ $$ \to $$ RCH $$=$$ N $$-$$ NH₂

What sort of reaction is it?

Which of the following compounds can be used as antifreeze in automobile radiators?

In the replacement reaction

The reaction will be most favourable if M happens to be