Is Request public?

Yes for as long its status is pending. At the moment of posting a 'request' the status of a request is 'pending'. During this period, Helpers can view the request and decide if they can and want to help. Once an Helper lock a request, the request change to 'pending-approval' mode and stoped being public for new searches of requests.

Note that request item may still appear on non freshed search results, while it was already locked by an helper, Yet other helper can't lock it.

How can I earn money with Requests.

Users can earn money by offering their help to users that post Requests, asking for help. You start by viewing available requests. Each request has a payment offer. Then lock a request you are willing to help with. You may set a bid either the same or different than payment offer.  Only one user can lock a request.  Once a request is locked, requester required to either accept or reject the locking helper. If you were accepted, you can collaborate for solving the issue, or maybe you need to make some tasks.