We can't do static linking with Qt librarires if we are using LGPL licence,if I understood right.What about doing static linking with third-party librarires using LGPL licence?

Also,I heard that all Qt commercial licenses are perpetual,and they include first 12 months of maintenance and support.So,if we buy a commercial licence now,can we freely(without paying additional money) upgrade to commercial Qt 6.0 when it becomes available?