Chuck writes: "I replaced some old iron pipes a while ago, but I didn't replace the pipes going from the basement up to the second floor bathroom because the pipes are embedded in the wall."
If those vertical pipes are strapped into place, you will have to open the wall, at least part of it to release the grip. If they jog with elbows, you are dead. If however you are able to cut off the pipes at the top and the bottom, and find that they will move freely, you can succeed in replacing them without opening the wall. The trick is to get the new pipe to follow the path of the old pipe.
Free the old pipe but don't remove it yet. Take a strong rope that will fit inside the pipe. You can either run it right through the pipe, or make a special "connection" on one end. The special connection is simply to tie a knot in the rope, shove the short loose end into the pipe and bring the knot up tight to the pipe. Use duct tape to attach the rope to the pipe. The knot will help to make this much more solid than if you did not have the knot.
Now bring the old pipe down, with the rope attached. You will probably have to cut the old pipe several times to get it all out of the wall. You should now be left with a rope strung through the pipe pathway. Attach it in the same manner to the new pipe. If you are using rigid copper, you will have to solder joints as you move the sections into the wall, so don't run the rope through the pipe, it will melt -- attach it to the lead end. If you are using flexible plastic, it will just follow the rope. If you are using bendable copper, you can straighten it out as it feeds into the wall. In all cases, it is the joined rope that will feed the lead end through the old pipe pathway. Don't use it to pull hard or you may pull the rope off the pipe, push the pipe up and have someone on the top who is using the rope to just guide it along.