IPhone Restore_ispw files

Those .ipsw are files used by iTunes when you do a Restore (or Update) on the iPhone. They are downloaded during the process. If you delete them, iTunes will download them again, if needed. So, it should do no harm to delete them manually.

Actually, you should only see one ipsw file on your phone, the one that is in place for you to restore your device if necessary. The others, at least on a Windows computer, are sent to the Recycle bin when you perform an update. If you are referring to the ones you see in the recycle bin, yes, you can delete them.

Indeed if you find more than one for a given device type, probably means you have not installed the latest iTunes, which only keeps the last version.

Only reason I can think for keeping more than one would be during the transition period in iOS upgrades. There you might want to save the previous version so you can downgrade while Apple is still signing the installer. The rest of the time, old installers are useless on non-jailbroken devices.

That is unusual, as they are generally sent to the Recycle Bin when you update your device. But, as others have already told you, there is no problem with your deleting them. Also, any of the older ipsw files that are no longer being signed by Apple could not be used anyway, so it is a good idea to get rid of them.

Yes, assuming the updates are installed on your device and you don't need to download them again.

You're welcome.