Which one of the following compounds will give an orange precipitate when treated with $2,4-$dinitrophenylhydrazine?

Arrange the following compounds in decreasing order of reactivity towards nucleophilic addition reaction:
$I: HCHO$
$II: CH_3CHO$
$III: CH_3COCH_3$
$IV: PhCOCH_3$

Following compounds are given:
$(i) CH_3-CH_2-OH$
$(ii) CH_3-CO-CH_3$
$(iii) CH_3-CH(OH)-CH_3$
$(iv) CH_3-OH$
Which of the above compound$(s)$,on being warmed with iodine solution and $NaOH$,will give iodoform?

Which of the following is not a final product obtained by cross aldol condensation of ethanal and propanal?

Hex$-4-$en$-2-$ol on treatment with $PCC$ gives $'A'.$ $'A'$ on reaction with sodium hypoiodite gives $'B',$ which on further heating with soda lime gives $'C'.$ The compound $'C'$ is $....... .$

What reagent and/or reaction conditions would you choose to bring about the conversion shown in the image?