Did you search the manuals (link at the top of the page)? They will tell you answers to all three of your questions if you read.
It is not mandatory to unpack a packed file before sending it via FTP, but the data in the file must be transferred as binary and will be totally unusable on the other end until it is unpacked (and good luck with that if the other end is not a z/OS machine since it will need conversion from EBCDIC to ASCII once unpacked).
Can u provide some more information on packed files.
There is a link to the manuals at the top of the page. Find the ISPF User's Guide manuals and look for packed in there.
I will provide references to the manuals, but it is a waste of my time to regurgitate what the manual says, especially to someone who has not bothered to follow my earlier advice -- I did not say to search the forum, I said to RTFM.