Can the executer of a will refuse to give the beneficiary their inheritence?

Absolutely not. And take note, no one is an executor until they have been appointed by a court. The will must be filed in probate and the court will appoint the executor. Once appointed the executor must settle the estate according to the provisions in the will and the state probate laws under the supervision of the probate court. Any executor who fails to perform their duties according to the will and the law can be sanctioned by the court.