If you want it closed, Fandom will get around to that eventually. If you want to expedite the closure, just contact staff. Otherwise, you could use it as a test wiki but then the name might be an issue. Staff might be willing to move it or they might just close it and tell you to open a new wiki as your test wiki. I am not sure which they would do. The last option I can think of is unlikely but, if there is a topic that could use the same name and you are interested in, you could repurpose the wiki.

Well, then I guess your only options are to either use it as a test wiki or have it closed. There aren't really a whole lot of options for what can be done is abandoned wikis.

Yep, I even already said that either the wiki is open for adoption, or staffs may delete it.

Still, I'll contact Staff though