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 is built to be reflective of the site as your user experienced it at the time of their session.
If your site is updated, replays of sessions that took place before the site update will show the old site look. Conversely, replays of sessions that took place after the site update will show the new site look.