opinions

well it depends on your skill with champs that you pick but IMO playing support is the best way to ensure that your adc gets going and for the most part when your bot lane does well the rest of your team will do better and the jg can ignore bot and try to help out others so i think playing supp is the best way to help ensure winning

Really anything not named Support. Mid can roam and shuts an enemy laner down, the jungler is all about objective control, roaming and shutting down enemies, the ADC mows down objectives and can really pump out damage consistently in teamfights and top lane, while not the best position to carry from, still has impact and the benefits of being a solo laner.

Carrying has a lot more to do with consistency, shot calling, play making and NOT BEING KILLED very often.

Jungle Ganker. Gank their noobs. Get fed, destroy enemy morale.

top,mid,

jungle only if you are not a tank

Adc, jungle, top and mid. With no particular order.