1. This file is responsible for maintaining the package's dependencies of all libraries the project is going to use.
2. You can point to them using extends in the tslint.json file, as follows:

{
  "extends": ["tslint:recommended", "tslint-config-prettier"],
  "rules": {
    "array-type": [true, "generic"],
    "no-string-literal": false,
    "object-literal-shorthand": [true, "never"],
    "only-arrow-functions": true,
    "interface-name": false,
    "max-classes-per-file": false,
    "no-var-requires": false,
    "ban-types": false
  }
}

3. Testing first generates a lot of benefits, such as the ability to anticipate acceptance criteria, better narrative understanding, and safer refactoring. This is because once a test is passing, it's safe to refactor it. Also, TDD results in more tests and consequently results in longer test run times and fewer bugs.
4. Postman is a Google Chrome app for interacting with HTTP APIs. It presents you with a friendly GUI for constructing requests and reading responses.
5. You should add the proper HTTP status code in the response methods.
6. It means that those dependencies will be used only in the dev environment.
7. Mocha.opt are properties you can define when Mocha is running, such as --timeout 35000, --full-trace, and so on.