Taibaozheng Visas (台胞證)

Hello,

I am a US and Taiwan passport-holder. I have been living in Shanghai for the past year on a tourist visa issued on my US passport. It’s about to expire. I would like to re-enter PRC with my Taibaozhen. I know that you can get a visa on-arrival at the Pudong Airport but it’s only a single-entry 3 month visa. Is it possible to get a longer-termed visa with multiple-entry in Hong Kong? Is it even possible to renew the visa once in PRC?

*Related Question: I got a single-entry 3 month visa on arrival with my Taibaozhen at Pudong in May but I plan to re-enter with a new visa. Do I have to cancel the existing one to get the new one?

I hope I am clear enough to yield some answers. Thanks!

Steven