Python Pandas: Create a dataframe from CSV, update values in columns

I can read & correct the code, but got rusty in writing it from scratch.
Need help in writing a code for the following functionality (I will embed it in the master program):

Create dataframes
StatusGroup
USCISresponse
Use CSV as a source file (Log.csv) to append USCISresponse with a few modifications.
Add Index field
Add date/time of the import
by default: add manually in the code before the import
optionally: current date/time (comment the corresponding line in the code)
Update field "StatusGroup"
VLOOKUP from dataframe 'StatusGroup'

See excel file with data sample & table structure attached.
More requests will follow on the statistics and visualizations with the USCISresponse.

Please suggest time & budget requested.
Thank you!