Obviously you can. However, extended version of your paper should be substantially different from the conference paper. The title and abstract should be different. Moreover, there should be significant technical contributions in the journal paper. In addition, the journal version should be free from plagiarized contents.
I think you can but you should increase the content of your data in research article and give different conclusion otherwise it will fall in self-plagiarism
if you edit the paper according to the journal's format, than you could publish it in a relevant journal, but you have to mention that it was published first in a conference.
Obviously you can. However, extended version of your paper should be substantially different from the conference paper. The title and abstract should be different. Moreover, there should be significant technical contributions in the journal paper. In addition, the journal version should be free from plagiarized contents.