look under freelance^^
look under ad rater
Appen and Leapforce you have to study and take a test also sign a NDA. I know clients of both companies let's just say you know both of those companies too so they pay pretty nicely. You get two chances to pass the test.
They don't care what you think, they want to test if you can follow the guidelines. Answer according to the guide book and when asked to state why you think you are correct quote the page you got the answer from.
Since all these jobs are under freelance it is up to you to file your own taxes (
)and they can not supply you with proof of employment