You can start by talking about it on the development mailing list. If everything goes well you can start writing a patch to Qt and submit it to gerrit for review (open a feature request first is also a good idea so it helps keep tracks of it).
Alternatively, you can also create a Q64BitSpinBox (with a better name than that) and provide it as an add-on
If you write something yourself, you are the copyright holder, you can post it anywhere. The only exception is when you write something when instructed by a company - then the company (your employer) has the copyright.
The quote you provide means just that: you are not allowed to copy notes from somewhere else if you are not the author.
In general, you should start a new thread, if you have a new question. This new thread's shall reflect a very brief summary of your issue.
As indicated in the docs QFtp is an implementation of an FTP client. AFAIK it is working as traditional FTP clients. At least that reflects my experience. It has several "command line" commands as you know from linux and windows shells. So, if you like to get the file some place else, you need to navigate to this place and send the file. Checkout "mkdir,":http://qt-project.org/doc/qt-4.8/qftp.html#mkdirhttp://qt-project.org/doc/qt-4.8/qftp.html#cd and the other stuff.
Note: QFtp is deprecated and is no longer directly available in Qt5
Please, don't use the Qt Contribution forum for this kind of question, this one is dedicated to contributions made to Qt.
As for your problem, variant of this question have been asked several times already, search the forum for "network transmission" or similar key words.
Also, have a look at the Fortune Server/Client from Qt's documentation.