You can easily do so via the Admin Console – just keep in mind that changing from an annual plan back to a monthly one isn't possible once it's already started. Any changes from annual to monthly need to be made at the start of each new billing ...
It depends on your plan and your chosen number of active users. You can have up to 2k active users in Starter and Premium plans. However, you should get an Enterprise plan if you need more than 2k active users.
The most beneficial feature is that you can have up to 10x million active users. You will have custom XBlocks, advanced exclusive certificates, advanced analytics & insights, White Label Branding, and advanced support for training and onboarding as ...
The most important difference is that you get to Monetize your courses in the Premium plan. You also get the multi-language option, a custom domain, and single sign-on options.