The full offence need not be committed before a person becomes criminally liable - liability can be incurred at an earlier (or inchoate) stage
offences are often committed by two or more people who agree together to commit a crime - this is a criminal conspiracy.
if a person embarks on a crime but never completes it, it is possible that he or she has attempted the offence and will still be liable
a person might not commit a crime but encourage and persuade others to do so - they are accomplices but also may be guilty of incitement
https://www.kent.ac.uk/law/undergrad...l/inchoate.htm