Yes, you should also start at a beginer level
Cause you should know their proper stances and you might learn one or two things you didnt know, that way you can complete your own arts and decrease your weakness
It is their decision of how fast you adapt to things. I do kick boxing too for 6 months and TDK and they put me on a white belt LOL i learned alot by just being there cause the ranks differs from each other right? That means the teachings are also different. It is on their hands to decide if you mastered each level's teachings