Is it possible to get admission for bba last year after dropping my diploma in civil engineering, to save my years?
No! If you want to get admission in BBA then you have to take admission in the first year. There are no such lateral entries to save your years.
If you complete your diploma then you can go for BTech Civil Engineering based on the lateral entry exam which will give you a admission directly in the 2nd year of BTech.
I hope my answer helps. All the very best for your future endeavors!