Is there elevators to reach upper seats?

Unfortunately, no. Although there are wheelchair accessible seats. Also, the stairs are unusually wide, carpeted, and not steep, which I found very helpful, since I am recuperating from a knee injury.

Is the public address audible backstage?

Yes

Yes. Some few steps to reach foward seats in the smaller theater. No steps for tbe front row in the smallest theater. No steps for most of orchestra in thr big theater and the back of the balcony.