Is it okay to send a paper to a journal as well as for conference
Apparently conference has different meanings in different disciplines. In the fields with which I am familiar, conference publications are either limited to abstracts or are published in proceedings which are just as official as a journal In the former case there is of course no problem but in the latter sending the same paper off to a conference (for proceedings publication) and to a journal would not be correct. Therefore, you need to figure out what norms apply in your field, particularly whether the conference proceedings is a real publication.