I have 2 problems,just had my bathroom floor tiled on top of concrete floor and was going to use a outside 4 in outside flange on a 4in soil pipe. I can fit over soilpipe now but tile under flange bolt down holes have no concrete under them,plus top of soil pipe is 1/2 inch below top of tile ,tile is 1/4 in thick. What is best fix? Build conc. Up and go to inside flange or add extension to soil pipe .

You can use an Oatey twist-n-set inside the pipe and then add a flange spacer. Twist-N-Set® Cast Iron Replacement Closet Flange :: Oatey.com

What you're looking for is flange extenders, (see image) found in most big box stores. Good luck, Tom