`Ch_(3)-CH_(2)-C -=CH overset( R)underset(H_(3)O^(oplus))to` Butanone, R is

CH_(3) CH_(2) Br overset(AgCN) (to) A underset(H_(3)^(oplus) O) overset(NaOH, Delta ) (to) B , B is :

HO- CH_(2)-CH_(2) -CH =O underset(underset((4)Delta)underset((3)H_(2)O^(oplus))((2)H^(oplus)))overset((1)KCN)(rarr) (A), Product (A) is ,

CH_(3)-overset(O)overset(||)(C)-CH_(2)- overset(CH_(3))overset(|)underset(CH_(3))underset(|)(C)-CHO overset(KOH,H_(2)O)underset(Delta)to product (C_(7)H_(10)O) :

Choose the correct order of stability of carbocation using concept of hyperconjugation I CH_(3)-overset(CH_(3))overset(|)underset(CH_(3))underset(|)(C^oplus) II. CH_(3)-overset(CH_(3))overset(|)underset(H)underset(|)(C^(oplus)) III. CH_(3)overset(oplus)CH_(2) IV overset(oplus)CH_(3)

What is the correct order of decreasing stability of the following cations ? overset(oplus)underset(CH_(3)-CH-CH_(3) II overset(oplus)underset(CH_(3)-CH-OCH_(3) III overset(oplus)underset(CH_(3)-CH-CH_(2)-OCH_(3)