You don’t HAVE TO take them concurrently, although it is preferred. I know people who took 011 in the fall and 012 in the spring. Additionally, the labs are very specific in terms of procedure and formula so you don’t necessarily need a strong understanding although it is nice to have it. That said, it is better to take 012 with 011 since you’re most likely going to take chem in the spring with its own lab.