The correct expression is to go or be 'on all fours'. Note that there is an 's' at the end of the word - it is FOURS, not four. It means to be, or to move, on your hands and knees. Crawling, in other words. This is the only meaning of this expression.
I also found the very strange definition you mention about 'in conformity with', but it is only on Dictionary.com - no other dictionary has this definition. It's very odd indeed. I can only assume that it's some kind of mistake. Forget about it.