Yes you can activate Udp plan by sending sms code if you have sufficient balance in your account. You can also activate additional channels and also broadcaster bouquets. There will be no extra ncf.
If you want sms code, ping me on pm, I will share.
I think, as far as I know zero ncf an has been withdrawn for airtel black users, How ever zero ncf plan still continueing on users account.
I don't have info on Rc 400,you may check on app and also lcn 121.