Determine expected max aircraft speed, and engine thrust at that speed and when stationary.
Well, sort of. At the very beginning, you may know the desired thrust at a given condition, but you have to work all the way through the calculations to get the actual thrust at that speed. If the actual thrust and desired thrust don't match, then you would need to change the design assumptions (e.g. change fan diameter, or compressor pressure ratio or something) in order to meet that.
What I'm trying to say is, I think you may be combining the concept of how do I design a jet engine to meet a certain performance goal, with how do I evaluate the performance of a particular jet engine design.
To do the later, you start with upstream pressure, upstream temperature, and velocity, and the known design of your engine, and walk from front to back. At the end of that process you will know thrust, mass flow, fuel consumption, etc for that given design and operating conditions.
To do the former, you start with a set of assumption, calculate the performance, and iterate until you have the desired design. For a large commercial turbofan, this process would typically be done to optimize the performance at cruise (since that is where the plane spends the majority of them), and then you would verify that other conditions (e.g. sea level static takeoff) are acceptable.
