If i delete a movie i purchased on my phone can i still download it for free of itunes on my computer?

No, you only get one download for movies. Connect your iPhone to the computer you manage the phone with and use File > Transfer purchases from iPhone to store a copy on your computer. You can then safely remove the copy on the phone.

tt2

No, films are currently a one-time only download, so before deleting it from your iPhone you should copy it to your computer's iTunes first via File > Transfer Purchases - otherwise you will need to pay again to download it.