Note that the altmemphy add an AFI port, which is much simpler and now the default, so if you're re-creating the core you have to explicitly select non-AFI(assuming that's what you have.) If you have done non-AFI, I believe a few extra ports to interface to added features were added, but if you don't tie them off I don't think it matters.
The multi-corner analysis is not for any derating, but for a thing called temperature inversion. (Basically not all structures scale between max and min delays at the same rate, so it's possible to have paths make timing at both max and min but fail at this middle point). But I am pretty sure there is no derating done in the timing models, as I've seen it asked for and yet never received. (Note that it's probably easy to do basic derating for the lab, but it's a whole other set of issues to derate and guarantee those numbers...)
Note that there is a setting under Assignments -> Settings -> Operating Conditions that allows you to change some PVT settings. For the life of me I don't know what these do and would love someone else's input. The best I can guess is they might affect power estimates.
