marcgrube
Hi
Let me reply you one by one on this.
1. Yes Guru will be updated for Joomla 4, it is under development and first there will be preview version release.
2. I suggest you to install Guru Pro as fresh since light version is old now and has many changes compare to Guru Pro
3. You can use PHP 7.x on current Guru version with Joomla 3.9.x
4. There is no such error, kindly check the demo site https://ijoomlademo.com/administrator/index.php
5. No direct link option is present, student must have to click on the lesson name to open it.
6. On course view there is option to show hide the sidebar, same for mobile view
7. Can you check the next button on our demo site and share the screencast of issue with a course view?
8. Only Lesson type quiz has option to submit the feedback from teacher view, i suggest you to look over the demo site to add it as it has Guru Pro version
9. Result can be seen on the backend as report section there is demo data for it. But main feature is on frontend as teacher login.