I'll be writing "Spinning Harakiri" as the Tekken 3 name from here on out which is "Suicide".
Harakiri - d+1+4
Is a stationary attack where it will attack whoever is behind Yoshi.
Meditation - SS+3+4
Is a sidestep type move where you display your back to the other player.
You are unable to do Harakiri in this state.
If you leave it going for too long you will lose the round. What you can follow it up with is...
Soul Siphon - 1+4 or 2+3
This move which continues from "Meditation" and turns Yoshi around and take health (or give health when you hold forward whilst doing it ("Possession")) to the opponent.
Fake Suicide - f,f+1+4 (while moving)
Does the entire move to suicide but ends with Yoshi showing his back to the opponent.
Suicide - f,F+1+4 (while moving)
This move does the full move of where Yoshi presents his back and ends with a Harakiri.
Double Suicide - f,F+3+4,f,f (while moving)
After Suicide you can add extra input to stab Yoshi again, if you fail at KOing the opponent you will lose the round.