If it a same company but contests hosted by different managers, you will have higher chances of many different terms. People as possible participants must read terms very carefully before joining if they don't want to miss important information. They can be disqualified by ignoring contest rules and this possibly causes initial fund loss by lack of carefulness for Reading before Joining.
This applicable to everything where an individual's participation is needed.
People who don't do their due diligence when participating in giveaways, contests, bonus and promotion offers miss alot, it affects their chances of winning and they are the first persons to feel that they have been cheated or that the system is rigged when in fact, the fault is theirs.
Therefore, in addition to betting what you can afford to lose, we should also add that reading before joining anything is as equal to this rule.