I was stuck at Bonetail for four days. Died 12 times, but I managed to beat the crap out of her. I wish I just grabbed the goodies at L90 and ran away :/
Just beat the pre Hooktail pit for the first time myself and wanted to see if anyone else had uploaded a successful attempt. Congrats on doing it! Bonetail really sucks and I definitely got saved by luckys and the extra milliseconds on superguards more than once. Anyways nice work and I wish everyone planning to attempt this good luck!
The only thing that you need technically is the ability to go into paper mode so you can slip through the bars to actually get to the pit. Obtain paper mode from the chest and hooktails Castle. After that it's pretty easy to get to about the 20th floor of the pit where you can obtain fire Drive, and that will take care of most things in the pit for you no problem.
This answer is pretty helpful gamefaqs.gamespot.com/gamecube/920182-paper-mario-the-thousand-year-door/answers/324084-preparation-for-pre-hooktail-pit-of-100-trials
I guess we'll just have to wait a few years down the road for a reliable switch emulator that allows is to use cheats to get to the pit during prologue so people can stsrt attempting that.
He probably just kept grinding. No matter what you always get at least one star point for every enemy you kill, and you only ever need 100 stars to level up so you could theoretically even grind to the max level in the prologue.