I think I will participate in review competition, what are the chances to take place? And if I can participate twice making 2+ reviews?
Very good chances to be in top 50. Tough to compete for top 5, but there is a possibility. To be elegible for rewards you need to write at least 5 reviews.
300$ will be paid in tokens , am I right ? What is a current token price in exchange with normal volume?
In RVN tokens. RVN is Revain's inner token and exists only inside the platform. You can swap RVN for R tokens
https://coinmarketcap.com/currencies/revain/