if l am getting keam score 204 out of 600 , will l get admission in government controlled self financing colleges in state merit quota or management quota and what will be my rank .

As per your marks and merit and management quota, your rank lies between 15001 - 20000. It may go up given your reservation.  This is based on the previous year cut off. It may varies due to various reasons such as students response to colleges, number of candidates appeared, question difficulty levelThe KEAM cutoff will vary based on the institute, course and the candidates category. The expected cutoff of KEAM for General category is 50% whereas for other categories like SC/ST/SEBC is 40%.
https://engineering.careers360.com/articles/keam-cutoff