re: "I could not find a way to email support or any information about membership pricing"
It is not Upwork's intention that you email questions to Customer Support. Options for contacting Customer Support include creating a Support ticket, using live chat, phone.
But the best way to ask questions such as yours is right here in the Community Forum.
re: "Can you please tell me if I can accept contracts all over the world?"
Yes.
re: "I am currently in Grenada. Are there restrictions based on citizenship?"
Residends of Grenada are allowed to use Upwork and are allowed to enter into contracts with users from all over the world - from any place that allows Upwork to be used. Which is MOST places. (This page notes: "The US government says [Upwork] can’t allow users on [the] site from: Cuba, Iran, North Korea, Syria or the region of Crimea." And at any given time there may be a few others, primarily due to limitations on available payment withdrawal functionality.)
re: "I also would like to find out about any forms I would have to fill out for taxes if necessary."
Upwork does not require you to fill out tax forms for each individual contract. There may be a single form that you need to fill out as part of the onboarding process. https://support.upwork.com/hc/en-us/articles/211063948-Form-W-9
For example: I have personally used Upwork for over 7 years. I had to fill out one tax form to use Upwork. People who live in other places may have other forms to fill out, such as for VAT.
Aside from that, your interaction with taxes and forms is not through Upwork, but is based on where you live, and doesn't go through Upwork.
