Can I add one simple product to more then one configureable?
You can do it, in theory, at least directly in the database, but you may expect weird reporting results in the best case.
Magento is not supposed to be used on that way. That use-case is kind of "hacking" Magento and abuse of simple / configurable products. I strongly recommend to you to make new simple products in that case.
Yes you can and Magento supports too.
Same kind of implementation even I did in my few project.
One of best example is, service kind of simple product, like "warranty" (where inventory management required).
But it will be good practice, create separate simple SKU's for each config use to avoid report and product management conflicts.
@Sinisa I agree with you.
@ShoaibRehman89 I feel question is pretty straightforward.
Even in case of bundle/grouped, can we map 1 simple product with multiple bundle/grouped product?
Yes, you can. That situation is natural to grouped and bundle products, since they represent collection of other regular products. As I mentioned, it's not that you cannot do the same for configurable (although you have some restrictions in the Admin regarding that), it's not natural, neither logical.