Is it possible that admin can only submit the answer?

Yes, it can be possible by disabling answer form.

To disable the answer form for the frontend, set the following configuration to No

Stores > Configuration > Magediary > Product Questions > Answer > Show an Answer Form : No

• Related Articles

• What happens when customer report abuse answer?

  On submit the report abuse answer by the customer, admin gets an email notification and take steps accordingly like disable the answer.

• Can auto-approve the answer on submit by the customer?

  To auto-approve the answer, set the following configuration to Yes Stores > Configuration > Magediary > Product Questions > Answer > Auto Approve New Answer : Yes

• Where can I see like, dislike, report abuse answer log?

  Admin can see track record of like, dislike, abuse answer activity from Marketing > Product Questions by Magediary > Activity Log

• Who get the email notifications and when?

  Admin gets email notification on Customer ask a question Submit the answer Report abuse answer Customer gets email notification on Submit the approved answer of asked question

• When does the admin get an email notification?

  The admin gets an email notification when The user submits a new inquiry. The user submits a new reply to the submitted inquiry.​