@Cheolf Thanks for your detailed answer, it left little to be questioned. I’m also relieved to hear it! I appreciate the help you gave. :’)
@Gumbymom Math 254 is one of the prereqs I need to take in order to take Differential Eqs 
. Some UCs require it for a letter grade but I’m applying to the ones that don’t. I asked the counselor before if I could take it P/NP and they said as long it’s not your major classes, it’s ok. But I’m curious now what you meant by not taking required prereqs as P/NP o: ? Because if so, I might decide to take it for a letter grade this time around if necessary.
Thanks to both of you for answering and have a nice evening!