Mary Cooch (personal account)

Hello there! You need to create your h5P questionnaire in the content bank accessed from the navigation drawer (the left side block) and then you will be able to locate it when you add an H5P activity. See the video in the docs page H5P activity

You can add a message to that effect yourself when you post the initial question, perhaps. (That's what we do when we do training with Q and A forums)

You have to wait the maximum editing time for forum posts which is by default 30 minutes. (Can be changed globally in Site administration >Security>Site security settings)

https://docs.moodle.org/311/de/Arbeiten_mit_Dateien_und_Verzeichnissen#Systemweite_Einstellungen
Vielleicht hilft die Dokumentation?

If by guests you mean non-logged in users, I don't think it is possible to allow them to upload assignments - and although I am not a programmer, I feel it could be a security issue if you did allow this- what could they potentially upload? Hopefully others with more knowledge will give a more detailed response. ( I am moving this to the Assignments forum where it is better placed, by the way)