I forgotten my Yahoo! security questions and answers, how can I get back it?
I would fully expect that you cannot. That would be terrible security.
The whole point of the security questions is to help you in case you forget your password.
Remember: Yahoo has no idea who you are until you login in. Could you imagine just anyone being able to say to Yahoo: "I am Inusah. No, really, trust me. I don't remember my password or the answers to my security questions. Can you give them to me?"
Further research reveals that Yahoo no longer uses security questions to help secure your account. They have almost certainly been deleted from your account by now.
From Yahoo! Help:
Security questions are no longer used for verification. Delete them if they haven't been removed automatically.
The security enhancements they do use are similar to Google: mobile phone numbers and/or third-party email addresses. When you log in from a device that's unrecognized, you can get a code sent via text, a phone call, or an email message with secondary information in order to log in.
If you haven't set that up, and you are having trouble logging in, follow the guidance at Fix problems signing in to your Yahoo account.
There's a problem with being unable to retrieve your security Q&A. Yahoo has revealed that in one of their multiple security breaches your Q&A probably were stolen. If you used the same Q&A on any other websites your security might be compromised there as well. But if you cannot recover the now-deleted Q&A you have no way of knowing where you might be compromised. Epic fail, Yahoo.