I understand that most schools don’t let freshman directly stay in a dorm with a sophomore, but are freshman and sophomore dorm rooms mixed together on the same floor?
It really depends upon the college.
And it also depends on the dorm within the university sometimes.
that is really school specific - my college tended to put freshman and transfers together so we had a wide range on the same floor. Also look into living learning communities and see how they do things which is possibly different.
Back in the day, my college mixed all “grades” together.
Now they have freshman dorms. I see that as the current trend.
Notre Dame still mixes all classes together in the same dorm. It’s very school-dependent.
Nobody here can answer this as it depends on the college and the dorm. Look at the Residential Life webpage of the college you are planning to attend and there are often details given for who can live in the different dorms – or you can call Residential Life at the college and ask.