Meh. He, like many other Hitsugaya haters, are just salty because he is called a genius but loses all the time (which is false as the only person IIRC he lost to was Aizen. Everyone else were either a tie or he actually won).
If you watched the video where Hitsugaya went into his adult form you can see how his hatred of him blinded him. Saying that his petals were a timer and called it an asspull when it was never stated it was a timer. It was only theorized by Shawlong.
Infinite. You mean 2? The first time in SS and the 2nd time in the fake town. That's it. You say it like it's a bad thing when everyone loses to Aizen.
Because he hasn't mastered it? He literally says that everytime he goes Bankai. He himself doesn't what happens (not until he mastered it in the TYBW). Also, if you watch the fight with Shawlong, his petals disappeared and his whole body bled up. Not confirmed that is what happens when his petals disappeared but closest thing to it.