#1
Since I moved to another country I used to play guitar through my laptop using Guitar Rig as software effects and common computer speakers. Well, enough with that crappy sound, I decided to buy a new amplifier, Blackstar HT5 head+cabinet. Anyway I like the effects I use and want to keep guitar rig software with all the presets I have created to use with my new amplifier. I will buy Presonus Audiobox 22VSL audio interface as well. The question is how to hook all the devices correctly in the proper sequence to not fry some of the new expensive hardware I'm going to buy? I'm in doubt about 2 possible configurations of the chain:
1. Guitar-->Amplifier input-->Effects loop send-->Audio interface input-->Audio interface output-->Effects loop return
2. Guitar-->Audio interface input-->Audio interface output-->Amplifier input
Which one is the correct? I guess the number 1 but I'm not sure.
2 more points:
1. On the rear panel of blackstar head there is a effects loop switch to set the effects loop to either +4dBV/-10dBV to use, say, with professional equipment (+4dBV) or guitar level effects such as effect pedals (-10dBV). Which setting should I use if i plug the audio interface in here?
2. The audio interface has stero output with 2 separated channels (L and R), so when i link the output to effect loop return wouldn't be any issue to use just one channel (say L channel)?
Thank you very much to anybody could help
#2
I think nothing will get fried in any case, but the correct chain is #1 because this way the valve preamp of the head receives a clean signal from the guitar. This is what this preamp is intended for and I wouldn't put anything before it, unless it is an EQ or a compressor.

According to the ht-5r handbook, the effects loop is mono, so there is no way you can use stereo signal unless you buy two amps. Just set up Guitar Rig's output signal to mono. You can use the left output of the interface for effects return and leave the right plug disconnected, it will not harm your interface. Never do this with speaker plugs, it can overheat your amp.