WO2014201088A1 is not a patent. It is a published international application, which can never issue as a patent. It has entered the national stage in the US as Application No. PCT/US2014/41863, and is currently pending.
I think your situation is this. Claim 1 of the prior art reference gives a method of 4 steps. You perform all 4 steps in your method. Claim 4 of the prior art specifies how the fourth step is done; you do it differently in your method.
Assuming your judgment that your steps are identical is correct,
1) Generally yes, you will be infringing claim 1 of the prior art. If their patented method comprises 4 steps, then any other method comprising those 4 steps as recited would infringe claim 1.
2) Yes, every method which includes the 4 steps recited would infringe claim 1.
3) If you add a step between 3 and 4, but still perform steps 1, 2, 3, and 4, then you will be infringing claim 1.
In this case, you may be eligible for a patent if your new step makes a novel, non-obvious method; however, if you do get a patent, the prior art (assuming the application issues as a patent) would block you from using your method without a license. (If the prior art inventors wanted to practice your method, they would also have to obtain a license from you in this case.)
4) Yes, if your method adds a fifth step to claim 1 which is not disclosed in any prior art reference, then your method would be considered new.
5) If you use only 3 of the 4 steps recited in claim 1, then your method would not infringe the prior art reference. In this case, a patent issuing from the prior art reference would not block your patent or require you to take a license, since your invention is outside the scope of their broadest claim.
You can't not infringe a patent by taking the invention and adding something else to it. If you improve it, you may be eligible for a patent yourself and will be able to block others from using your improvement, but you're still practicing the original invention - just in an improved form.
Think of patent rights like property rights, where you have a right to keep others from trespassing, but not necessarily a right to walk on your property. If you own a piece of land (a patent for your new and non-obvious invention), someone else who owned a ring of land surrounding yours could block you from access to your land - it's yours, but all paths to it lead through private property. You cannot access your property without their permission (getting a license) to pass through their property. Similarly, if they decide they want to cut across your land (use your improvement to their invention), you can block them or force them to take a license.