Need some suggestions regarding no last name & its solution.

I need some suggestions regarding adding partial name change. My name in all documents, gov ID including educational certificates is single word having no last name. I did not add surname in my name during 10th board registration & now the same name in my all matric, intermediate, degree certificates.
Correction in name in government ID like PAN, Aadhaar is not big problem for me, but  not possible to change the name in my all the educational certificates. It’s tedious job.
In online applications, forms do not proceed without last name, in that case I have repeat my same in the last name blank. But this not solution & work in all applications.

Same thing happened to opening PayPal account, no submission without last so I had contact PayPal support & they processed the application manually from their end. HDFC bank also took like 10 days in opening account the reason was they have to take some approval to open an account with single name. The they told me for security reason. IDK what security issue here.
So I want last name included officially in my name to get rid out last name jhanjhat. But I worry to do bcz educational certificates is main big issue.