1
Want — have a desire to possess or do (something); wish for. Need — require (something) because it is essential or very important rather than just desirable. The definitions reflect how we commonly distinguish between these terms.
2
Each and every are both used with singular nouns to indicate quantity. Each indicates two or more items, whereas every indicates three or more items. When three or more items are involved, we tend to use each when we are thinking of the items individually and every when we are thinking of them collectively.