Can The Police Make An Arrest Without A Warrant?

Yes.  If a person has committed or is suspected of being involved in an offence that is classified as a cognisable crime and police investigation of the case leads them to believe that the suspect is guilty, then the police can arrest that person without waiting for a magistrate to issue a warrant.

The police must always give proper reason that is preferably backed up by some sort of evidence when arresting a person . If someone is caught in the act of committing a crime then the police can arrest them immediately and without a warrant as well.

Keep in mind that just being named in an FIR is not reason enough for the police to arrest you. The lack of this knowledge by the general public is often misused.

If someone is named in an FIR the police must conduct preliminary investigations and collect some real evidence against the person before arresting them.