Session replay is an add-on feature for paying customers only. You may try the feature for free for 14 days or 10,000 sessions (whichever comes first), after which you must contact Sales to continue use.
Session replay is for Web only. Native mobile (Android, iOS) session replay is not currently supported but is on our roadmap.
Session replay works out-of-the box with all Single Page Apps (SPAs), including Angular and React. SPAs are handled the same way as non-SPA applications, where the URL change is saved as a new pageview.
SPAs use browser history APIs to modify the URL, which triggers changes in the DOM content. Session replay listens to these browser API calls and all DOM changes and captures the URL changes and the content. Heatmaps, which rely on session replay, follow the same logic.