juniors

In theory all of the sororities are "open" to it. However, a few only take one or two Juniors.
Alpha Phi is very closed to juniors, so I would let go of wanting them unless you are related to someone from their National Council.
All the rest of the houses take juniors.
Lots of people go through Rush as juniors, and most end up in "middle tier " houses.

A few end up in top houses and a few end up in lower tier. Overall, it is worth it to go through.

Loads of people go through as juniors. It is a tiny bit harder but not much. You will be fine.
I do agree with what the person above said about APHi. They do seem to be filled with almost all freshman.Some nationals make them take all freshman. Luckily the rest of the houses are fine with it. You will find a home.