To download the installer, use the Reflect Download Agent that you can retrieve from the link in the “Installing Macrium Reflect” KB article linked below. However, if you’re having auto-start issues, you might want to choose to remove scheduled tasks during the uninstall, in which case you’ll need to set up your schedules again. There’s no need to remove your license if you’ll be reinstalling it on that same PC. Image Guardian will be removed automatically. Uninstalling Reflect just involves uninstalling it like any other application. But if you just let the 20-second counter expire, the backup will start automatically.
If you’re referring to the postponement dialog, you can click Cancel if you don’t want the backup to run, or OK to skip the postpone, or specify a postponement period. Not sure what you mean about how many seconds you wait before pressing Enter.