Selecting an ontology methodology for developing ontology

My question is that is it mandatory to follow any ontology methodology while developing an ontology?

As per my understandings:

1. You can develop an ontology without following any specific methodology
2. You can strictly follow an ontology methodology according to your need/context of your ontology/project.
3. Instead of strictly following, you can partially/ loosely follow an ontology methodology according to your need/context of your ontology/project
4. You can even merge steps from multiple ontologies according to your need/context of your ontology/project.
5. One cannot say that one methodology (i.e NeOn Methodology) is better than another one. you can select any methodology according to your need.
6. Ontology Development Guidelines and Methodology are same things.

Please comment/guide me point by point. Thanks.

Here are some examples of scientific papers about ontologies construction. These are not "mandatory" but good guidelines indeed.

Kolas, D., Dean, M., & Hebeler, J. (2006). Geospatial Semantic Web: Architecture of Ontologies (p. 1‑10). IEEE. https://doi.org/10.1109/AERO.2006.1656068

Denaux, R., Dolbear, C., Hart, G., Dimitrova, V., & Cohn, A. G. (2011). Supporting domain experts to construct conceptual ontologies: A holistic approach. Web Semantics: Science, Services and Agents on the World Wide Web, 9, 113‑127. https://doi.org/10.1016/j.websem.2011.02.001

Tan, H., Adlemo, A., Tarasov, V., & Johansson, M. E. (2017). Evaluation of an Application Ontology. In CEUR Workshop Proceedings (Vol. 2050). Bolzano, Italy.