skullaccio

The tasks are always the same. What may happen is that sometimes they take away the game from the website, so you can't complete more tasks from there. Once you completed a task, you can't go back to it, nor can you re-do it to earn more SG. Hope I answered your question =)

What happens when we mark a normal comment as spam by accident? I did this already 3-4 times

you get very few xp from commenting on chat. When you're in higher levels you earn less XP from comments, so the forum is good for early lvls only. In my experience, the best way to lvl up is by playing games. You earn WAY more xp that way and lvl up quickly.