This task can done using css and media query only

Your task in question 2 is to create live connection (a socket) between tab4 to tab1 , tab2 and tab3.

(tab4->tab1, tab4->tab2, tab4->tab3) and check how it behaves with the data. For connection you might want to use some kind of framework and you have all kind of right to use it except you can only use JS framework. In this question you can use any JS framework, like Socket.io , Swr, Ajax etc.