Can I individually assign assignments to students rather the whole class!!??!
No, it will have to be whole class.
When I have a class with students at different levels, I sometimes make two assignments, and just check that the more advanced students did the more advanced assignment.
Or, I avoid the issue all together and just assign XP.
One final thought: I do this for Stories and for Tinycards -- You can tell your individual students to send you a screenshot when they have such-and-such a skill golden (or to red, or whatever).
Hope this helps!