Your account is bound to the instance you created it on. You can go to any instance you want, however you'll need to sign up again if you want to browse from say, kbin.social, instead of using lemmy.world. Regardless, you would see the content from both because they are federated together.
You can view and interact with Beehaw directly from your .ca account. For example, you can go to lemmy.ca/c/technology@beehaw.org and post/comment, etc. It's defederated from .world, so people on that (this) instance can't anymore.
You are seeing the ghost of the beehaw community prior to defederation. The only updates to that ghost (i.e. new posts or comments) will be from fellow lemmy.world users. You won't see new content in that community from users of other instances. Also other users won't see the content lemmy.world users are posting to the ghost. The ghost is effectively now just a private community of lemmy.world users that is beehaw in name only.