The first is what it says, default inheritance is protected. Fix it by specifying public
The second one is about an attempt to use the constructor of CMessServSess which is explicitly declared private. As it is Symbian C++ code, you should use CMessServSess::NewL/C instead, which is public.
class CSessionObserver : public CBase, public MMsvSessionObserver
The third one is about using a non-static member. ThreadFunctionL is a static method, it has no object context. iStat is not static, it would be a member of an object.
Generally I would suggest removing the threading part from this code, there is no reason for having a thread in this code.