If I am caught in such a situation, how am I to know which police station area I am standing in?

You can dial 100 and share your location with the officer at the other end of the line and let him or her guide you to the nearest police station. Or, you can get in touch with any police officer you see closest to the spot and ask for help. Cops are bound to act irrespective of jurisdiction.

Was it right for the Maidan police station officer to refuse to help citing jurisdiction?

No. Ensuring the safety of a person in danger is the immediate priority of the police. No cop can shrug off the responsibility on the ground that the spot of action is in a different police station area.

Did the officer intervene finally?

Yes, he did. But the fact that he had initially refused to act citing jurisdiction shows he was unaware of his duty and responsibility.

The Telegraph

The youths were not wearing helmets and were driving recklessly. Was it not reason enough for the police to act?

Yes, instead of waiting for the youths to flout more rules such as assaulting a person or heckling a woman, the bikers could have been prosecuted for not wearing helmets, reckless driving and for riding a bike in a group of three. Youths riding bikes without helmets and sometimes three or four on a bike are a common sight in the city. Police should act suo motu in such cases.

The youths have told the police that the app cab hit one of the bikes and damaged its looking glass, so it could have been that the cab driver was at fault.

Even if the version is correct, that did not give the youths the right to take law in their hands. They should have noted down the registration number of the vehicle and lodged a police complaint. The police could have subjected the app cab and the bike to mechanical tests to verify the claim and the counter-claim.