I know the game is old, but I just started playing. The tips above still work, except for the PVP chest. I couldn't get it. I only built one castle to level 99999999, and it's stuck that way even without using Game Guardian.
Following the same logic of freezing time, you can automatically level up heroes in training, reaching level 500 in a few minutes.
I'll try the PVP chest again. My problem is that, unlike the other timers, the PVP one doesn't stop when I open Game Guardian.
So far, 2 weeks without a bam.