Instead of cholent I want to make meat for shabat lunch. Can I put meat in raw just before shabat or does it need to be 1/3rd cooked? If so why Thank you

The accepted custom is that it must be 1/3 or should even be half cooked before Shabbat. That opinion which you mentioned should just be relied upon in extreme circumstances (say you suddenly found out at the last minute that you need to be home for Shabbat).