however, if i add aux bus it dosen't appear in aux window.i still only see 4 nus routes. is this normal?
You can create more than 4 'returns' in the Aux/Master/Tempo Pane, and those will be visible. However, you're still limted to 4 Aux 'sends' per-track in the Track Inspector. Right-click on a track's Aux
X Send control to shift it towards a newly-created buss return.
also if i add 21 under the other option in the audio settings, it always gives me blue screen. just 21.
I can't help you there. It sounds like some sort of mismatch between available and actual outputs, but I've never seen that happen myself.
also, i have in the 4 aux bus window, master and master2. is that correct to be there?
In your own configuration, probably yes. It will depend on the number of 'master' outputs exposed by your soundcard. Others will see a single master output; still others will have three; I happen to have 16 master outputs available. When your soundcard is detected by Project5, the number of master outs is configured, and it can't be changed by the end user.
The 'formula' to determine which ReWire outputs are which for a particular system, in order of appearance:
The number of Master Outputs + the number of Aux (return) Busses + the number of tracks in a project.
In your case, the first two ReWire slots are your Master Outs, the next four are Aux Busses (assuming the default 4), and that's followed by your tracks. Track#1 would be Output#7 from ReWire's perspective. If you add a fifth Aux Buss, Track#1 would shift to ReWire Output#8.