Thanks for your reply!
Re bug 2), I guess it may happen in China area. As in China I have paid for a mms service called Mobile Newspaper, everyday I can receive 2 mms which has news contents mixed by Chinese articles and pictures, something times it could reach 20 pages per 1 mms.
So when I have 3-4 mms remain in inbox, and when I open any one, and start viewing, after I finished I want to click the inbox button to return back and read another mms, but it can't return to inbox.
But I have think out a way, when I face this problem, I click the "inbox", if it doesn't work, then I click the "i" button (information about swirlymms), then it will return back.
I think this problem maybe not popular, since I have found a way to solve this case, you can ignore it.