Omega v18 Help

I Have Samsung S5 G900I 4.4.2 and downloaded the v18 5.0 Lollipop, I want to know if I need to download stock 5.0 for me to flash omega v18 or can I just flash it without the st ock 5.0

Change from CM11 (4.4KK) to Omega ROM (4.3 JB)

I would like to change the ROM in my Xperia T from CM11 (based on 4.4 KK) to Omega ROM (based on 4.3 JB). How could I install this ROM ? Are the any tutorial to downgrade from 4.4 to 4.3 for Xperia T ?. Also the CWM I have is V6 and I have checked that this ROM requires the CWM V7 or V8 to do installation. Where could I get it ? Thanks in advance.