retreat- means withdraw like in war retreat the army form war zone or u can say difficulty or danger situation m retreat krna .
retract->means withdraw but in this time (statement, opnion, promise, decree(order))
revert-> means return to previous state or some times called come back , go back ex- if u are buying fruit form market and once u got rotten mango immidiately u revert back mean (wapas lota dena) but generally it is convention never used the word bac with revert bcz revert words itself contains back. so here get back him means return so c answer. but be carefull 'get someone back' means revenge to someone