@nrajesh - There isn't any such service in general. You could check it for each API with what status it returns, but there is no dedicated service to see if the API's are up and running or down. Or may be, as a last resort - you could check with the Support. I hope this helps.
... View more
@nrajesh - Yes, you do not need to store the refresh token, if you already have it. It will not be expired until it is blacklisted or refreshed using rest API call. Here is an article for refresh token which will give you more info regarding the refresh token.
... View more