“I can’t even find out the member login area to test the password resend email button” – it should be the same page that always, isn’t it? just copy URL of the page to be able to open it and do the test.
” I don’t really understand how to move the widgets before switching” – not move, just open https://lady***a.com.tw/wp-admin/widgets.php page before activation other theme and pin it, after doing tests and activation XStore back, go to Widgets page in a new window and compare content on widgets area. In case some widgets changed their positions, you will be able to set them as it was in the pinned tab.
One standard license is valid only for 1 project. Running multiple projects on a single license is a copyright violation.