Version is the fifth core element. It is not always needed. If different versions of the source exist, use this element to state which version is being cited. Some examples of different versions include editions, director's cuts, and abridged or unabridged versions. Apps are also treated like a version in MLA style.
Edition:
Howard, Rebecca Moore. "Avoiding Sentence Fragments." Writing Matters: A Handbook for Writing and Research, 2nd ed., McGraw Hill, 2014, pp. 600-10.
Rowley, Hazel. Franklin and Eleanor: An Extraordinary Marriage. Kindle ed., Farrar, 2010.
MLA Handbook. 8th ed., Kindle ed., Modern Language Association of America, 2016.
Abridged/unabridged:
Sewell, Anna. Black Beauty. Unabridged version, F. M. Lupton, 1877.
Director's cut:
Scott, Ridley, director. Alien. 1979. Performance by Sigourney Weaver, director's cut, Twentieth Century Fox, 2004.
The information above is mostly adapted from IRSC Libraries.