I just realized, GS send me back to classic theme when accessing Groups, even with Qvitter as default. It would be different if I opened each individual group, all sent me to Qvitter.

There are some features not available in new GS but classic which I can't find link to them in new GS, like Bookmark or Messages. People might miss those features. In other hand, there is a feature can only be accesed in classic but the link featured in new GS, like Popular or Groups.

After trying to find out these difference, I discover something interesting.

All features in new GS menu always take place in the theme, except the unavailable ones. All features in classic GS menu send to new GS, except the unavailable ones plus another exception: Favorites.

In new GS, I can use Favorites from sidebar or my profile page. They all redirect to same link, same page. In the classic, it has same link but the page shown in classic. If open in new page or refresh it, it comes back to classic one.

Another worth mention is a pair of feature which I thought the same: People (classic) and Users (new). It seemed the same list with different sort but I checked manually, the classic one has someone not in the Users. I still don't know those functions, what make those different.