can i restore iPhone without backup

You can restore as new - which means setting it back to how it was when new out of the box. All your content will be wiped from it and you can then set it up fresh.

Without a backup, that is your only option.

There should be two buttons next to the picture of your iPhone. Restore from backup and it will have a backup time selecting icon next to it, and a button below it (I think) that says restore as new device or something like it. Click on the latter and I think a verifying packages and things like that will come out. Keep the device connected until it completely reboots and you unlock the device.

Yes, if what you mean is you want to set up your iphone like when you bought it, you can use th Set up as a new device button instead of clicking restore from backup.

By the way, if your iPhone has problem syncing over wifi, plug the USB cord in your computer. It will then back it up, if that was your problem.

Does it show an error message? If so, i think you should type error message --- for example 440 and there will be a page for it.