Add features to Google Sheet (20 columns)

I have created a google sheet with 20 columns. I want someone who is an expert in Google Sheets and Javascript to add features such as: >Adding default values only to records being added >Sheet-wise Unique value generation >Dynamic dependent drop down boxes, >Calculations on multiple columns based on subset of data in the sheet > etc Please only serious experts familiar with advanced google sheet features should bid because this is a test and small part of bigger project that you will subsequently be working on.