1 and 2. You must create custome commandbars class:

class CCommandBars : public CXTPCommandBars
{
 DECLARE_DYNCREATE(CCommandBars)

 virtual void GetHiddenControls (CXTPToolBar* pToolBar, CXTPCommandBar* pExpandBar);
};

IMPLEMENT_DYNCREATE(CCommandBars, CXTPCommandBars)

void CCommandBars::GetHiddenControls(CXTPToolBar* pToolBar, CXTPCommandBar* pExpandBar)
{
 if (pToolBar->IsTextBelowIcons())
  pExpandBar->ShowTextBelowIcons();
 
  
 for (int i = 0; i < pToolBar->GetControls()->GetCount(); i++)
 {
  CXTPControl* pControl = pToolBar->GetControl(i);
  
  if (pControl->GetHideFlags() == xtpHideWrap)
  {
   CXTPControl* pControlClone = pExpandBar->GetControls()->AddClone(pControl);
   pControlClone->SetHideFlags(0);
   pControlClone->SetBeginGroup(FALSE);
  }
 }  
}
and apply it:

int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct)
{

...

// Initialize the command bars
    if (!InitCommandBars(RUNTIME_CLASS(CCommandBars)))
        return -1;
...

ps. be sure CXTPCommandBars::GetHiddenControls is virtual (see XTPCommandBars.h)

it was changed only in 9.10. If it is not so, add "virtual" keyword manually.

1. I make a commandbar with style of text under button, the text will disappear when button is in the expanded bar. Could I keep the text at this situation. (pic for your reference)

2. The expanded bar includes all the buttons that can not be displayed at the same line command bars, Could I limit just include itself button.