<<Worse tsundre ever. From what I know of her character she should be able to force Kohaku into changing her back despite being bribed.>>
Yeah, I'm not a big Akiha fan either, though she's crazy popular. I'm definitely an Arcueid and Hisui person. Also, once you get into the comedy Routes of Melty Blood, heck, in certain ways once you get past Tsukihime itself, all serious concepts fly out the window. Kohaku becomes such a ridiculous joke character that she trolls past the 4th wall all the time. And besides that, Shiki and co. don't actually want to hurt anyone...usually.
<<1)Her clothes grew with her, why? I thought she was injected, it would make sense if she was sprayed or if the drug was a solution that made contact with her clothes?>>
Yes, that's the joke. It makes no sense. Shiki and Arc point this out. Lol, in the game at this point, Shiki turns to Shion, but her brain has shut down from the stupidity of it all.
<<2)I couldnt help Kohaku mented she had a drug which she already named for shrinking. Will this drug make Akiha normal sized or even smaller or mini-GTS(Question to people who are familiar with the games)>>
In the game you just beat up Akiha and she's back to normal afterwards. I can't remember if they mention whether or not they just forced Kohaku to give in or it wore off, or if they say anything at all. No shrinking.
In either case, the below meme accurately describes just about anything having to do with any and all Melty Blood related events (and the Dead Apostle causing them) in all 4 of its game volumes:
