Miku MIku Dance (MMD) is a 3D animating programm., witch is used to make models dance, pictures or even to make short movies.
use pmd editor you can get it on youtube or vpvp wiki
PMD Editor is an application for MMD (Miku Miku Dance) where you can edit the models
you need pmd editor (and several tutorials XD)
.mqo is for metasequioa, Metasequioa is a program that can be use to create MMD models.
If you are using the regular MMD (miku miku dance) you cant but if you are using a multi model edition of MMD you can download new models.
yes its a common bug
If you are using the MMD multi model edition they should be in your MMD[insert version of MMD you are using] → UserFile → Model
if you go on google you can search for the mmd models which u will use and the motions (dances) they will do. I suggest going on deviantart.com for those. Then go on youtube and lookup tutorials on mmd.
Youtube "Miku miku dance"
You may have a very very old version i suggest downloading a newer version
It's freeware. Google it.