1. Download the file here
https://www.dropbox.com/scl/fi/q3r6gh3ghk71tca8k9poc/FFX2-Last-Mission-saves.7z?rlkey=f1uagbvi7h01xu4p4kqhksxwx&st=6swximo6&dl=0

Extract and copy it into your FFX2 Last Mission save folder

2. For 10th floor achievement simply loading the save should unlock it.

3. For 20th, 40th, 60th, and 80th floor killing the boss is necessary but don't worry because my character is ridiculously overleveled.
Move with the directional button, lock enemy with Z, attack with C.

4. For Tonberry achievement : kill 4 mega tonberries and 1 regular one, an item should spawn in the room. Pick it, achievement unlocked.
If you accidentally pick something and can't pick Tonberry treasure press V to open menu, go to items, dump something to make room. That's all you need.

If you want to get the achievement the hard way I use this guide :
https://gamefaqs.gamespot.com/ps3/643146-final-fantasy-x-x-2-hd-remaster/faqs/70315/introduction

Let me know if anything is not working.

Thank you very much and please hit the like button if this "guide" helps you 😂🙏🏻