Re: religion of prophet before Islam came
Ebionites are sometimes referred to as “Jewish Christians” - they consisted of those Jews who accepted Isa (pbuh) as a prophet. They were scattered by the Romans along with Jews, and one community settled in north-west Arabia. The cousin of Khadija (ra) who advised the Prophet (pbuh) when he was distressed after his first revelations was one of these Ebionites.
Eventually their community disappeared between 1000AD and 1200AD, most likely assimilated into Islam within the Muslim world and into other Christian churches elsewhere.