35m assigned language?

As a new recruit, it's possible but not necessarily going to happen. The Categories are the difficulty level, not the level of need. For instance, Japanese is a Cat 4 language but we don't need Japanese speakers like we need Arabic, Chinese, Russian, and Korean speakers.

What language? If that's the case, you may be able to schedule a DLPT once you get to DLI. I had a friend who was a 35M and they were already fluent in Spanish when they got assigned to the Spanish course. They asked to schedule a DLPT for Spanish and within a reasonable amount of time, they left DLI and continued on with their service. Ask your company leaders when you get to DLI. CAT 3 languages are a year long, but your instructors are mostly native speakers who aside from the language, teach you a lot of cultural and political aspects about the country to which that language belongs. Their personal experiences are very valuable to understanding the language. DLI offers some great courses and Monterey is absolutely beautiful. It can be tiring, but it's all worth it in the end. But if you feel you would rather test out and move on, do what you will. It is your choice.

You most likely not be assigned the language you already know but if you can prove that you already know it you can do one of two things. You can prove to your DS when you first get to DLI, that you know that language and he/she will change you to that class and it would be a easy time when you are at DLI or you can try to DLPT in that language but if you fall that DLPT test for the language then you have a good chance of being re-classed.