In what sense are you saying really? Like you register for them and you let them use the domain? But you still control the domain right?
No I register domain for someone else with their info for him and setup website in that domain for him and after that he is full owner of domain.
Yes that's perfectly alowed, just as long as you take off the payment information off the hosting/domain panels, as then when he comes to renew it'd be fraud as he doesn't have permission from you to pay for it.
You will be actual owner. If the person you register domain name for agree with that - go ahead that is not a problem at all.
If the domain is under your control you will always be the owner. You are allowed with his/her's permission to use there information to register the domain, which I won't suggest always better to use your information for legal reasons. As long as you have there permission you are able to use it.