About restoring newer ios version backup to an older version ios

Hi, i have iPhone 6 and its ios version is 12.5 and then my iphone 7 plus and its ios version is 14.3. I have the backup of my iphone 7 plus. How can i restore it to my iphone 6?

It is not allowing me restore it saying the backup is not compatible . Is there any way? I really need to restore it to my older mobile. Please help

Thanks in advance