Personally, I would just start a new discussion.
A good rule of thumb is to start a new topic for each 'theme' or 'subject'.
That way when others are searching for related topics they don't have to wade through unrelated topics.
BUT... having said that.
Yes, you can still edit your topic. (see attached for ref)
To edit a topic look over on the right and use the drop down menu to select 'Edit'.
From there... select 'Edit subject'.
Again, make sure you are in your original/first post in order to change the Topic title.
Editing the subject in a post will just create/change that posts subject title.
Regarding the skeleton tool... I had better let others answer that as I haven't dug deeply into that yet.
I use the Plastic Tool a lot and that (combined with standard keyframing of position, rotation and scale can achieve a lot.
Rigging of 2D characters is of interest to me but I'm mainly focused on old school traditional hand drawn and the near equivalent digital processes.
I'll get there eventually... when I have a pressing need for it! :)
But to answer your question... vector... raster... toonz raster... that should all be fine.
Again I use the Plastic tool to 'rig' characters but the Skeleton tool is a great way to do that.
Aside: My primary interest in the Skeleton tool is to quickly change between images onscreen without interrupting parent/child relationships.
(Can) opentoonz fill the Frames between 2 Frames automatically, if I move an object?
Sure can!
Vehicle and Plane movement is as easy as moving an object from point A to point Z.
OpenToonz will fill in the rest.
The powerful part of this is that you can then change the images that are referenced along the way to add cool effects such as jet blast, smears and blurs, etc.
Of course those effects can be added other ways as well but sometimes we want to capture some of that effect in the actual drawing itself.
Start a new topic titled "Planes, Trains and Automobiles" and we can explore the possibilities with some custom mini-tutorials.
I figure since I'm planning on testing out the possibilities it might as well answer other peoples curiosity also. :)