1. "During normal rounds, hacks only related to me(being a hacker or as a defender) will be shown." Is it right?

2. Why some people can hack other's code even not in the hacking time(During the contest in normal rounds, During the hacking-phase in edu/div.3) ? I'm curious about this. Is it intended or a glitch? Although, hacked solutions will keep AC verdict

I'm not experienced in hacking, so could anyone answer these questions?