All is not lost if you still can boot into download mode. Press volume up or down (cant remember) to continue.
Download a stock Rom from sammobile and reflash it in odin.should be able to boot up and run again.
U just put it to download mode. Now u just need Odin 3.09 and flash twrp, then just put ROM inside and boot to twrp n install.
yeah, assuming you're on stock everything:
1. Download odin 3.09 (google, but don't install the bloatware that comes with it), and the 4.3 version for singapore on sammobile if you were on android 4.3 version from
here. use the dropdown boxes to find the correct version. unzip the file from sammobile (you should get a xxx.tar.md5 file)
2. make sure kies is installed on your computer. so that your computer can read your device.
3. open odin 3.09, click ap and choose the tar.md5 file.
4. power off your phone (if in bootloop, remove then replace the battery). now hold these 3 buttons: volume up, home and power buttons. A warning should appear that you are entering download mode, press vol up to confirm. Connect data cable to computer and phone. In odin, a blue rectangle showing COM ## should appear. Make sure only auto reboot and F reset time are checked. Then press start.
5. odin will flash the stock rom to your phone and auto reboot it once its done. you should be able to use it properly.
if you don't understand anything or not sure what to choose, read the full thread
here
ask questions either in the qna part of note 2 in xda forums or here
