Hutong card

Sorry, you can only get the refund at the service centers in Beijing or through the App online. The international version of Hutong Card is called Beijing Silk Pass. I see other's share that he top up the physical card with silk pass app. You can have a try.

Using a transportation card in China is recommended. Yes. Most of Chinese cities offering, travellers are unlikely to save money with it. It is just for conveniency. For Beijing transportation card is needed more.

China is a huge country. China T-Union is just for using the card with leftover balance. Topping up outside the city is impossible. Getting a refund is same result. It's impossible out of city.

Silkpass is government side app which is not good enough. It requires either Chinese phone number or email address. Most of international email servers are blocked by China Great Firewall. Yikatong web site is also blocked by Great China Firewall. Registration should be avoided as much as possible anyway.

If you are thinking of getting a refund, then it is better to buy a basic Yikatong card, which is a loan card. You will probably get 5 to 10 Yuan savings with it.

Beijing Subway started accepting Visa or MasterCard as payment methods directly on ticket gates. But it is China. It may take more time to settle down. More successful reviews are needed to recommending to new visitors.