H4 Visa stamping

[Mohini4]

My son (5 years old)  whose h4 visa was stamped in 2017 as a dependent to his Father. Now I have a valid H1b visa and planning to travel to India with my Son. My husbands H1b visa is under transfer to another company. My Questions are -

1) My h1b visa is stamped and valid until 2021. Therefore if i take my son to India with me can i apply for dropbox stamping for my Son?

2) What is the process while scheduling an appointment for my Son? Do i have to create a account for myself and add him as my dependent before applying?

3) How to take pay visa fee for dropbox visa application?