Processing time depends on the encode settings and container used (they have recommended parameters to adhere to), as well as the size of the file. How heavily loaded YouTube is also matters. Could be minutes to upwards of a week, depending on all these factors.
You don't need to leave anything open; the moment the upload is done, it's all on YouTube's servers.
You don't need to leave anything open; the moment the upload is done, it's all on YouTube's servers.