If I unbind the device and bind it with another account, can I still see videos that were taken before?
Please note that videos do not get carried over to a different account. Therefore once you unbind the device from your original account and bind it with a new account, you can no longer see videos taken previously under the original account.
For example, if User A purchases YI Cloud Service with his/her account then unbinds the device later on from the account, User B can then binds with the same device however User B will not be able to see any videos taken under User A's account.
User B needs to purchase YI Cloud Service separately in order to enable the service under his/her account. User A after unbinding can still see the videos uploaded previously by navigating to "My YI Cloud" and selecting the right device.