Demiplane: let the door expire. Do I have a way of getting back?

Can only Monks use “unique” weapons or can anyone do that?

If a Warlock forgoes an attack to let his Pact of the Chain familiar attack does it occur immediately?

Do you think Uncanny Dodge halve the damage from spells?

Do you think Uncanny Dodge halve the damage from spells? The feature says Attack but dont mention Attack Action .tks