Let's analyze the nature of the offense.
Inchoate Crime (i): An inchoate crime is a crime that has been started but is not completed.
"Attempt" is a classic example of an inchoate crime.
Since A attempted to steal, he has committed an inchoate crime.
Impossible Attempt (ii): This is a specific type of attempt where the commission of the full crime was impossible due to factual circumstances unknown to the offender.
Here, it was factually impossible to steal the jewels because they were not there.
This is a classic example of an "impossible attempt," which is still punishable as an attempt under law.
Immature Offence (iii): This is not a standard legal term used to classify offenses in criminal law.
Therefore, the offense committed by A is both an inchoate crime and an impossible attempt.