divide and conquer and recursion

Usually, yes! Merge sort is an example of the same. Here is an animated version of the same.

Yes. In divide and conquer algorithmic technique we divide the given bigger problem into smaller sub-problems. These smaller sub-problems must be similar to the bigger problem except that these are smaller in size.

For example, the problem of sorting an array of size N is no different from the problem of sorting an array of size N/2. Except that the latter problem size is smaller than that of former one.

If the smaller sub-problem is not similar to the bigger one, then the divide and conquer technique can not be used to solve the bigger problem. In other words, a given problem can be solved using divide and conquer technique only iff the given bigger problem can be divided into smaller sub problems which are similar to the bigger problem.

A Divide-and-conquer algorithm is by definition one that can be solved by recursion. So the answer is yes.

"Always" is a scary word, but I can't think of a divide-and-conquer situation in which you couldn't use recursion. It is by definition that divide-and-conquer creates subproblems of the same form as the initial problem - these subproblems are continually broken down until some base case is reached, and the number of divisions correlates with the size of the input. Recursion is a natural choice for this kind of problem.

See the Wikipedia article for more good information.