Not sure what applies in Oz but in NZ we would do a boundary adjustment. Need services of a surveyor and lawyer. No reserve contribution required to local Council because you are not creating a new lot. Talk to a surveyor first.
Yes it's possible if your neighbour agrees to sell part of their land to you. I see this has happened many times in the past from the properties I have considered buying.
It varies state to state, some have restrictions on purchases involving land that is not yet registered and the seller has to meet disclosure requirements.