I did my BBA in the year of 2014. Now, I'm doing job and I wanted to continue my studies in external MBA. Is this MBA be valid or not?

The salary after MBA is mainly based on the rating or ranking of B Schools from where you have completed MBA. For example salary package IIM MBAs are much more than other MBA institutes. Like this every B School are ranked or rated on the basis of Infrastructure, quality of education, placement reco

You can do MBA by distance learning from a reputed Institute. It is not valueable as in campus MBA but it gives you a management degree which will help you in career growth.