resume command question

i was wondering - if i partially (or fully) download a file, and the file is then changed on the server - and i tell it to resume, will it download the changes? redownload the whole file?

and if a file is the same on my computer and on the server will it skip the file?

and if the files are the same size but are still different will it update?

If the file on the server is bigger you go to get a corrupted file. If no you can't resume.

well.... is there any way to make smart FTP download all files from all folders with a certain mask (like *.html or something)?