Visa dropbox facility to take admission in the same school and branch in Fall-2018, which I didn't join in Spring-2018.

I am from India. I have B1/B2, H4, F1 visa with no denials.
I was to take admission in Spring-2018, for which I got my I-20 and F1 visa as well. Due to the health concerns of my parents, I had to extend it to Fall-2018. I applied again in the same school and branch, now they have accepted the admission and issued a new I-20.

i) Can I use the drop box facility as mentioned in

Why do you think you need a new visa, has anyone advised you to get one? Unless validity date of the Spring 2018 F1 visa stamp ended, which is not possible, all you need is a new I-20 for Fall 2018 and evidence of active SEVP record. A letter from DSO will be helpful at port of entry but is not required

Thank you Sir.
Even I was thinking so,
some friends advised me to take an interview again.

But, while filling up the appointment form, it is asking to
take up drop box, which confused me.

Thanks for your clarification.

Please be careful of bad advice. If they are friends in India whose visa was denied, they are just envious. If they are friends in the US, then they don’t know the rules well enough. Either way, anyone giving you such advice needs to understand that if you did go the embassy and apply for a visa second time (drop box or in-person) and it was denied, then the denial will have legal superiority over all other approvals on file. I am very happy that you thought of asking the question here. Have a safe trip to the United States!

Did you attend any visa interview?