There is a repository on a GitHub account and also another Github account linked to Heroku. Can I link multiple GitHub accounts to my Heroku account so that one application can access a repository and access another repository with another Github account?
It is not possible to use multiple GitHub accounts with one Heroku account. I would recommend giving access to the target repository to the same GitHub account. If that is not an option, then it is also possible that you could have two Heroku accounts, each of which maps to a specific GitHub account.