(aka Jeong Daesang -- other names)
Korean professional, b. 1957-09-08
7p 1996-01-01 
8p in 1999, or on 2000-01-01 
The Korean Wikipedia article has some modern information for the Korean speaker: "2016년 삼성화재배 월드바둑마스터스 본선에 진출했고 2017년 시니어바둑리그 준우승을 차지했다. 2018년 제5회 대주배 본선에 올랐다.".
In 1989, Cheong reached the semifinal of the 4th Korean New King?; like the Shinjin O and Xinren Wang this tournament would've probably been restricted by age and rank -- though at 31 it would be hard to call him a young player at that time, so perhaps it wasn't. He had beaten Lee Changho in the quarterfinal, and had also reached the quarterfinal of the previous edition.
Go Ratings has him apparently highest ranked at the beginning of 1986, when he was 28, at #233. However, less than 230 professionals are listed in their rankings prior to that year, so it can't be said for sure when his exact rating peak was.
According to Go4Go, Cheong's spent his career after 60 playing almost exclusively in the Korean Senior Baduk League?. Earlier in the 2010s, he used to play in the GG Auction Cup and Daejoo Cup, both for senior Korean professionals. He was still playing in the Maxim Cup for Korean 9 dans at least as late as 2010.
 The KBA page provides plenty of information on various occurrences to do with Cheong between 1984 and 1996, but since neither numerals nor 단 (dan) occur in the text, it doesn't seem to shed light on his promotion history.
 With the note "승점획득", which looks to have a meaning like "acquired by his number of wins". The use of 점 is unclear.
 Based on the text "1999년 : 8단 승단. 제18기 KBS바둑왕전 본선, 제4회 삼성화재배 본선". However, he didn't win the 1999 KBS Cup (that was Cho Hunhyun). He also wasn't the runner up: although the KBS Cup article didn't have that info, Wikipedia says that that was Lee Changho.
The date of 1999 was also given by Charles Matthews on the original 2002 version of the article. However, the KBA page also supplies the date 2000-01-01. Perhaps he earnt the promotion in 1999 and it was awarded at the start of 2000.