Can we collaborate with cross-functional team members for a task? How can I add followers to a task?

Yes. You can collaborate with cross-functional team members by adding them as a follower to the task. 

To add the followers to a task, perform the following actions:

1. To add followers to the task, navigate to Tasks and open the particular task for which you want to collaborate. 
2. Click Followers tab, and click Add Followers. 
3. In the search box, enter the name or employee ID and select the required follower from the search results.
4. Click Save Changes to add the follower to the task.