A few questions regarding features

Hello

Thanks for your interest in Opigno.

Here are some answers to your questions

Moodle has quite a few more question types than Opigno, but the only one that I'm really missing, is the Numerical Question (i.e. the user answers with a number and a unit of measurement and the system accepts the answer as correct, if it doesn't deviate from the correct values by more than a pre-specified amount). Is something like this possible in Opigno?

This question type does not exist in Opigno

I would like to offer free courses, but have the users pay for receiving a certificate (this seems to be a pretty common procedure in many learning plattforms). I could not find a way to set this up in Opigno... Is it possible?

You can have people pay to access the course, but the certificate is free. To have the course freely available and pay to download the certificate you should have some customizations done on your Opigno instance.

In most of my courses, the students will be allowed only two attempts at the quiz and will have a time limit. Unfortunately, the way the lessons/quizzes are presented in the interface makes it far too easy for them to accidentally start the quiz: E.g., clicking the link in the overview block (on the left side of the course page) automatically starts the quizz (the link that ends with "take"), which - in my view - is definitely not what the user would like to do when clicking that link. I think it's more likely that the user would just like to be presented the quiz page and then having the option to click on "Start now". Can this be implemented?

This was initially like you describe in Opigno, but we got a lot of complains from customers that there was some useless clicks that are bad for the user experience. And I do think that these clients were rights. That's why we adapted the navigation to be like it is now. To do what you want some changes in the code are required. But I think it won't be good for the user experience.

Is it possible for the questions in a quiz to be presented on a single page? Jumping around via the buttons on the bottom (or the dropdown on top) doesn't seem very user-friendly to me, especially in a stressful setting like when taking a test.

Yes, you can use H5P content type "Column" for that

The courses that I would like to offer in the LMS will repeat each year. Now, I would like to set it up so older students (who have already taken the course) have access to all lessons in a course except for the quiz. Students, who take the course for the first time, on the other hand, should only be presented more lessons as the course progresses (e.g., via the availability options), but should be allowed to access the quiz. In Moodle I can do this by using groups in the courses. Is something similar possible in Opigno?

This would require some custom developments in Opigno

Is it possible to require the students to stay in a "Theory" lesson for a pre-specified amount a time (say, 30 seconds), before the lesson will be counted as "passed"?

This would require some custom developments in Opigno

Is it possible to print some code on a certificate and allow for verifying that certificate code via a simple link? This could be useful, when a certificate is presented to some future employer.

You can print whatever you want, but you would have to implement the function to generate the code !