Can I assign only guided reading mode?

Yes, you can assign only Guided Reading Mode to students.

When creating the assignment, choose "Yes" on the "Enable Guided Reading Mode?" toggle and choose "Do not assign assessment questions" from the Assessment Options dropdown.

You can enable or disable Guided Reading Mode on existing assignments using the edit pencil icon in the top-right corner of your assignment. You cannot edit which assessment questions you assigned to students however.

Assignments with only Guided Reading mode will always have annotations, read aloud, and translate enabled. These features cannot be disabled at this time.