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