How to Downgrade 3Gs from 4.3.5 to 4.3.3 for repair No service

For downgrade 3Gs from 4.3.5 to 4.3.3 we need to Download:1- 3Gs 4.3.3 firmware from Here2- Ireb4 from Here 3- Tiny Umbrella from Here4- Snow Breeze 2.7 from Here Now after download all Follow these step,s 1- Run Tiny software and connect Tethered jailbreak 3gs on ver 4.3.5 and save SHSH files, software should save shsh files for 4.3.5, 4.3.4, 4.3.3, 4.1 ver. 2- Now run Snow breeze and select