The process by which a heavy nucleus splits into light nuclei is known as

In a nuclear fusion process,a certain mass of hydrogen is converted into helium,resulting in a mass defect of $0.02866 \, u$. The energy released per $1 \, u$ of mass formed is ......... $MeV$. (Given $1 \, u = 931 \, MeV$)

Which of the following statement$(s)$ is/are correct?
$(1)$ The rest mass of a stable nucleus is less than the sum of the rest masses of its constituent nucleons.
$(2)$ The rest mass of a stable nucleus is greater than the sum of the rest masses of its constituent nucleons.
$(3)$ Nuclear fusion involves the fusion of two light nuclei to form a heavier nucleus.
$(4)$ Nuclear fission involves the release of energy by the splitting of a heavy nucleus.

Explain the process of thermonuclear fusion as a source of energy in the Sun and stars.

Which of the following statements is correct?

What is nuclear energy?