Please help us help you and fill where relevant: 
LimeSurvey version:LimeSurvey Community Edition Verzió 6.15.4+250
Own server or LimeSurvey Cloud: Own
Survey theme/template: fruity
==================Hello All,
 I need to create a multi-level permission system and two plugins were recommended for this:- ResponseListAndManage- TokenUsersListAndManage
Unfortunately, I can't install either of them because they are not compatible with my version, which is 6.15.4+250. What do you recommend? Should I go back to version 5 or what should I do? Many thanks

Both use public view, then unsure it work on 6.
You can test adding   at gitlab.com/SondagesPro/TokenManagement/T...g.xml?ref_type=heads

If it don't work, surely to update HTML part.

> I need to create a multi-level permission system

Can you put more information ? If you do not need user management: maybe you can try without updating using TokenUsersListAndManage and reloadAnyResponse.

Else : the plugin developer offer services : www.sondages.pro/contact.html

Thank you for the advices. I don’t know the exact requirements of the user permission system yet; for now, I would just like to test the possibilities.
BR