No, you need an article in front of "Treasure Hunt." I'm assuming this is referring to a specific treasure hunt, so in this case it would be "The treasure hunt...." "and has selected the most valubale folk treasure in Shenzhen." this part is unclear. Does "the most valuable fold treasure in Shenzhen" refer to what is being hunted? if so, you could say something like "The treasure hunt was held in SWIJC on the 21st of April, 2011 and featured the most valuable folk treasure in Shenzhen."

They are all OK, but they do not mean the same thing.

"has" is an auxiliary verb indicating the passive or, as another user mentioned, the present perfect.

it is hard to identify the meaning without the context. it could mean someone works for the next 8 days OR they might be referring to the expression "eight days a week" which just means that they are extremely busy

it's actually not a grammatical error, "broke" is being used here as an adjective describing the person's status (of not having any money).

nut traces are undetectable remnants of nuts. for example, someone with an extremely severe nut allergy could have a reaction from eating food that was prepared using the same tools that were used to prepare nuts. that would be an example of nut traces.

actually, using the third person in your example is more CASUAL. it makes sense at a party setting, but it is not appropriate for formal or written English.

"quarter" is no longer used in this way, although it once was several centuries ago. it no longer means the same thing though. if you use "stage" it would mean more that the house is artificially set up to LOOK like someone lives there.