1. Do you know why the "list values" is disabled from my end?
List values is disabled because field list from previous tool which is connected to Q is taken as list values.
2. How can i change the data type as string for all for user selected fileds?
Unfortunately, there is no easy way to change datatype of only the selected fields.
What you can do is change datatype of all fields to v_string perform join then use autofield to convert them to proper datatypes. It would be something like below.
Hope this helps : )