If I store Bitcoin in Trezor and eventually I lost the device, can I retrieve the Bitcoion to any other wallets, including online wallets like Mycelium, using the master seeds.
You can import your seed words to any other wallet supporting BIP39 default trezor format, but it wil become hot wallet if you enter to Mycelium or other software wallets connected with internet connection.
Can I access my Bitcoin from elsewhere using my master seeds?
Example, I'm in Capetown and my Trezor wallet is in Miami, USA. How do I access the Bitcoin without the Trezor physical wallet if I needed money urgently?
Location is really not important and you can carry your wallet or seed words anywhere with your, even in your own head if you have good memory.
Since it's more like a flash drive, I guess, what happens if it got corrupted by viruses? Or any malware?
Trezor can't get corrupted by viruses because it's not connected with internet, and it's not used for data storing like regular usb drives.
However, there is chance that some keylogers and viruses are installed on your computer that can steal anything you type with your keyoboard.