I have Maxthon 3 and prevent it from updating by disabling the update file. Maxthon 4 may also use this file but I'm not sure.
The file is called MxUp.exe and can be found here, (assuming Maxthon is installed on your C drive)...
C ⋙ Program Files ⋙ Maxthon3 [or Maxthon4 if you have that ] ⋙ Bin ⋙ MxUp.exe
The file can be disabled by renaming the extension. This way you can prevent it from running and also still find it should you ever need to re-enable it.
Renaming the extension is simply a case of replacing the .exe with something else, .unused for example.
You may get a warning when you do this, advising you that the file may become unusable if you change the extension name, but as this is what you want, you can ignore the warning.
IMPORTANT : If you do not see the filename extensions when viewing your files in Windows explorer, you will have to change the folder options.
Open your Control Panel and click on Appearance and Personalization, then click on Folder Options. In the Folder Options dialogue box click on the View tab. In the window, Uncheck the Hide Extensions For Known File Types option, then click OK.
Previous versions of Maxthon can be found HERE.
If you want a more specific version of the browser, I think PaulTon knows where these can be found.