In which case did the Supreme Court declare that "Secularism" is a basic structure of the Indian Constitution?

In which case(s) did the Supreme Court of India give for the first time the doctrine of ‘basic structure’ of the Constitution?

The landmark Supreme Court judgment that propounded the Doctrine of Basic Structure of the Constitution of India is:

In which of the following cases, the Supreme Court of India enunciated the ‘Doctrine of Basic Structure’?

The service conditions of the judges of the Supreme Court are decided by which Article of the Constitution?

Which Article of the Constitution of India deals with the Appellate Jurisdiction of the Supreme Court in connection with Constitutional Cases?