"Peter never plays."
Translation:पीटर कभी नहीं खेलता है।
You're allowed to drop होना if (and only if) there's a main verb and the sentence is negative (i.e. नहीं is in there).
For example: मैं दिल्ली में नहीं रहता is fine; you're allowed to drop हूँ. However, you can't say मैं एक लड़का नहीं because there's no other verb there. You must include हूँ. Make sense?