Code Snippet (Chrome Extension):
chrome.proxy.settings.set({value: {mode: "fixed_servers", rules: {singleProxy: {scheme: "http", host: "IP", port: Port}}}, scope: "regular"}, () => {});
Moderately, if from trusted sources. Always use HTTPS and antivirus.
Use tools like proxy-checker.net. Aim for <100ms latency.
Try another from the list or check your firewall. Update frequently.
Not fully—they're faster but less encrypted. Use together for best results.