Do I have to change the article name when it is the extended version of my published paper?
Usually, there is no formal requirement that the title has to be changed. In fact, if the journal paper is just the long version of the conference paper, I would recommend not to change it, so that the connection between the two papers is obvious to people who see the paper in a list of references.

As soon as the journal version of the paper has appeared, it is generally assumed that this is the version that should be read and cited, rather than the shorter conference version. By keeping the title unchanged, you tell readers that there is no need to read the earlier one as well.