Absolutely, as far as your plugins support for it. Example: You want us to install and set up plugins A, but to use plugins A you need to buy plugins A license.
Depends on the additional feature that you request.
An example that we do not charge you: Connect your site to MailChimp, connect the online payment to Stripe, set up a notification when someone buys, etc
An example that we may charge you: Creating costume conditional logic when someone buys, Creating a costume dynamic thank you page on one thank you page, etc
You need to finish this project in 3 months. Base on our experience most of the delay issues come from our customers. DeskTeam360 waiting for the contents, lack information about the site, etc
We will extend the project duration to an additional 1 month and you will not get a 10% cashback. More than that we love to re-negotiate, the goal is we love to help you to get to your dream site and have a better experience with DeskTeam360.