Well. we can help a bit there...

1. People post with their characters, perhaps occasionally being guided towards some goal by the GM.
2. Some RPs move quickly, others not so quickly. Free-level RPs tend to be the former, while advanced is generally the other way around. Casual RPs tend to fill the big, gaping hole between the two others. So the answer in general is that it is not necessary to post every day. You may risk being left behind by the others in some of the faster RPs, but most tend to take into account that people have lives outside the guild and come from different timezones.
3. That cannot be answered with a single answer. Some RPs end because players leave, others because the story is over. Others end for other reasons. 
4. Plagiarism is not appreciated here. If an idea of yours is stolen, contact one of the moderators. They can deal with it.


oh, and we'come to the guild.