Generate Safari Developer Certificate for building extensions I have gone through this link.But everything seems to be changed.
Everything redirects to Apple Development Program.So is it mandatory to enroll in that development program to create a safari development certificate to create extensions?

And if so where can I get that certificate from?
Apple unified all the developer programs (iOS, Mac and Safari) under one umbrella program entitled Apple Developer Program. This is what you need to enrol with to obtain a certificate for Safari extensions.