I was bitten by a monkey in my childhood, 20 yrs ago. can i get rabies or herpes simian b virus after 20 years due to that bite?

Almost no chance: There are a very few cases of delayed rabies in the international literature, although the exposure history is uncertainly documented. see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3424805/ Human infection by herpes simian b virus is even rarer and there is no evidence that it lies dormant, but that disease appears within 2 days to 5 weeks from exposure. See https://www.cdc.gov/mmwr/preview/m