👻_I_DU You can extend once per entry. The requirements to extend are pretty much the same as you submitted to embassy initially. There might be slight variations at each Immigration Office.
Currently, you would only need to show again for an in country extension at an Immigration Office. Yes, an IO could, at their discretion, ask upon entry. It has been reported but very rare and sources are not 100%
Once more as you seem incapable of understanding English. The visa a dependent of a DTV holder is issued with is a DTV visa. They do NOT get an "O". Now get back to your bottle or you will be having the DT's not DTVs.
It is well known about a DTV dependent visa. The dependents get a DTV too. You stated an O visa as dependents on someone's DTV. I really do not think you are playing with the full deck. Stop consulting with the Leo and Chang.