OPPO 205 Digital set up

I just received my Oppo 205 and have a few questions about setting it up, and need information on some choices in the set up menu. I running it with a Marantz 8802A . I amusing the 7.1 and 2 channel analog connections via RCA to the 7.1 connections on my Marantz.. In the 7.1 configuration I am using the 2 channel analog outputs to the FR and FL of the 7.1 configuration. My questions are the following of which concern the choices in the set up menu:

1- I receive 5.1 for movies and SACD's but cannot receive any 7.1 for movies? Not sure if I dont have somethingset correctly in the Oppo.

2-HDMI AUTO FORMAT- choices LPCM, bitstream, Auto?  

3-STEREO SIGNAL-Front Left/Right or Down Mix Stereo    

     not sure what this is about? or really how and what it effects

4-HDMI SPECS--1080p, UHD24HZ, UHD or UHD HDR   (I set mine to UHD HDR on a non 4K TV)

I love the video and sound quality. I was really impressed and it blue away my Rotel 990 cd player and my Pioneer DV 47A SACD playerwhich were pretty decent stuff 20 years ago. OK I'm a little slow to catch up and replace my gear!!   thanks in advance for your advice.