Some VPNs (thankfully not the ones I've listed above) could be risky. Limited server connections, slow speeds, and data sharing are all commonplace and it's crucial to select a service which offers a more basic version of their service or which doesn't offer data-sharing.
Many free internet providers provide an insufficient number of servers. This could lead to an overcrowding of servers, and your internet speed could slow down. Some providers even offer your information to be used to advertise in bulk. Choose a provider with an audited, independent, and reliable no-logs policy.
A VPN that supports Bitcoin payments as well as double-hoping and decrypts traffic is also a good choice. This will help you avoid the most serious problems caused by free VPNs. They are prone to a lack in security protocols as well as inexperienced to deal with DDOS.
Some VPNs for free have all the features you require. Windscribe, as an example provides a vast number of servers across 10 countries and is able to be used in a completely anonymous manner. It also allows you to connect to unlimited devices and unlocks a good amount of streaming content, including US Netflix. PrivadoVPN is another great choice with the ability to stream Netflix, Hulu and Disney+ and has a generous 10GB bandwidth limit. It's also user-friendly and has intuitive apps for all major platforms.