1. Correct, a beam with a cantilever extension is normal. Such a beam is always fixed through the cantilever side support. If you want a fully fixed connection both beam and column should be lateral members with full fixity. For gravity framing, a fulcrum…

If you are modeling the section using small shells and if you support multiple nodes at the end with nodal restraints, then you will effectively be creating a fixed end condition. Pinning a single node at the centroid of the shape would be one way to…