How to use ember-2-legacy?

We have the post in the documentation for Ember 2.16 about addition deprecation ember-2-legacy:

Ember 2 Legacy until: 3.4 id: ember-2-legacy Ember provides ember-2-legacy which is an addon to help app with deprecations during the transition from the 2.x series to 3.x.

https://deprecations.emberjs.com/v2.x/#toc_ember-2-legacy

We also have some configuration in README:

In ember-cli-build.js you can specify a config for ember-2-legacy

https://github.com/emberjs/ember-2-legacy#what-deprecations-are-covered

So, as I understand, if we specify some flag with false, like this:

new EmberApp(defaults, {
  'ember-2-legacy': {
    'enumerable-contains': false

then this particular feature will be off in ember app.

Should my App raise some error or notify me by console warning? In general, I have a case of all flags false and all tests passed, so my question is: is it mean that my application has no those deprecations usage cases?

Shall I keep ember-2-legacy with config in ember-cli-build.js til Ember upgrade 3.0

or

case with no errors on CI build means that: my App already has no deprecation and I can remove this addon at all?