I'm under the impression that Ponchi may not be too happy with people apparently only caring about Seihou because ZUN once made music for it, so making it obvious that you're probably only interested in the music might not be the best way to approach him about these things. You have to show interest for the whole thing.
If a fluent japanese speaker wants to contact him about this that would be great, but please word your e-mail carefully because we probably only have one chance of getting the C60 trial of Kioh Gyoku from him. I also recommend posting here before e-mailing him, since him getting e-mails about the same thing from two different people would be really weird. I kinda doubt he will upload the trial, specially considering that it's something that was once sold, but I guess you never know.
As for the Shuusou Gyoku prototypes, they're probably a lost cause at this point. Only people who were members of Amusement Makers at the time are likely to still have a copy, and these copies are most likely stored in old floppy disks or hard drives where they may be difficult to access. If you just wanted to hear Frontal Attack you're probably not missing out on much. ZUN probably didn't think highly of it since he didn't post it on his site along with the other two titled tracks. It's likely just a very short boss theme. Personally I was more interested in the prototypes for the gameplay and story changes.
So, a trail with exclusive music to it? There was version 0.01 of Touhou Perfect Cherry Blossom with something like that that surfaced at one point, which sported different music from the final game. If the case is the same with Seihou 2 here, I wouldn't be the slightest bit surprised.
You're thinking of the Trial+ version of PCB which was released at C63, pretty early into development. The biggest changes in the music were mix changes, the base compositions themselves didn't change much. The Kioh Gyoku trial is different. ZUN stated that the tracks had changed a lot, to the point where they could be considered different tracks.
Say, in the future is there a chance that the MIDIs you used for the recordings get uploaded for download? I feel like the original MIDI sequences would be neat to have for some people as there are those who like to arrange MIDI or try soundfonts for them, and you have to admit, ZUN's work with the sequence especially nice. Thanks in advance for your answer.
These MIDIs were made only for listening, they were never intended to be modified. Generally speaking, if something is packed inside a .dat file or similar, there's a good chance that the developer doesn't want you to be messing with it or using it elsewhere. Packing files isn't just for optimizing disc usage.
In any case, using MIDI files is a crutch. They limit creativity. The only thing you need to know about a track to start arranging it is the melody, and that's usually not too hard to sequence by hear. Nothing else needs to stay the same as the original track, and any mistakes you make while sequencing could become inspiration for your arrangement, or even inspiration for a new composition.