If one masturbates and doesn’t allow it come out, he stops it by any means and after some duration of time the person sees there is no ejaculation even a single drop of it, is that person pure and can he offer salah or it will be wajib for him to perform ghusl.

Answered according to Hanafi Fiqh by Darulifta-Deoband.org

بسم الله الرحمن الرحيم

(Fatwa: 275/270/H=03/1437)

Ghusl shall be wajib if semen leaves its place with lust but the person stops it, though no drop of semen is seen. His salah shall not be valid if he offers salah in the same state without performing ghusl.
هكذا فى الدر المختار (وشرحه الفتاوى رد المحتار ج 1 ص 108 (مطبوعه نعمانيه)

Allah knows Best!

Darul Ifta,
Darul Uloom Deoband