This is a bit tricky because the answers are not really as simple as true/false.

A) Token values are usually set with Assign Token Values activities, but in some cases they can be created or modified by other activities. For example, Read JSON/XML can store values to an existing token.

Additionally, many activities will create their own Token values that can be used within the workflow. For example, Find Entry will generate tokens for name, path, and more, and Token/Date Calculator can create custom named tokens of their own without Assign Token Values.

B) Tokens can have the same values, but they might not. If you create a token in your workflow with a static value, then any instances that run with that version would have the same value.

However, the tokens for each instance are independent and specific to that instance, so the values can be the same, but they are not "shared" variables so they can also differ.

C) Yes, but the Assign Token Values activity is only needed for custom tokens. Sometimes you don't need to create a new token at all and can use auto-generated tokens (check the Token Dialog).

For example, you can use tokens directly from Retrieve Field Values, or Retrieve Business Process Variables, and many other activities like Token/Date Calculator without Assign Token Values.

D) Yes. Every workflow will have some default Global Tokens available like DateTime, WorkflowInstanceId, etc., but some are not always populated. For example if there is no starting entry, the associated tokens would be empty.

Additionally, just about every activity will generate some token values of their own; think of tokens like the process and activity variables associated with each instance of a workflow.

Most token values are not saved in the instance history unless you use Track Tokens, but it should be used sparingly because tracking more tokens can affect the database and performance.