First export and mixdown failure

I have roughly completed a project with 50 tracks some midi some audio some instrument…When I exported to mixdown and completed the process only some of the tracks show up. I don’t believe that it is recording the instrument or midi tracks.Any suggestions? It may have something to do with the outputs.I have four of them and can only choose one at a time.I would like to mixdown the whole project to one stereo recording. Is this possible?
This is my first attempt at this.

HERE’S a picture.

If you want to mixdown one stereo recording, then obviously all tracks that you want to be included, have to be routed to one stereo output. Are they?

That’s what I’m beginning to realize.That I made the mistake of using more than one output for my project…I was wondering what routing the 50 tracks on different outputs would do when I first started out because some of the other 4 outputs I experimented with sounded clearer or louder than the first or second output.So I just kept the routing as it stood into 4 seperate outputs using some tracks in output1 others in 2 and so on…This I guess was a mistake for export mixdown because I cannot check all the boxes in the channel selection in “Export audio mixdown”.Cubaseai8 doesn’t have the “batch” option.

I routed them all to Stereo Out and initiated mixdown but I keep getting cpu useage overload warning and I start over and gets a little farther but then I gave up because the warning keeps showing up.

Got it going now …rerouted all to Stereo Out…but upon playback after mixdown It came out with different mix(some tracks louder than other -uneven).also real time option in mixdown export caused too much cpu warning and aborted mixdown so I unchecked the box and it works now.