Which of the following carbocations is most stable?

Here, (1) is stable because it would not change to other stable carbocation. It can only change 2∘C⊕ to 2∘C⊕ On the other hand, (2) can change to two 2∘C⊕ structures, Furthermore, (3) is stabilised by 1 ,2-Me shift and (4) is stabilised by  1 ,2-H⊝ shift.So (1) is most stable.