1. by that time we can definitely use Sun as a receiver's lense 2. 1 ton is starting from 1000 ton rocket. The Saturn V and Startship are on the scale of 5000

1. by that time we can definitely use Sun as a receiver's lense 2. 1 ton is starting from 1000 ton rocket. The Saturn V and Startship are on the scale of 5000 ton and assembled on Earth. That interstellar rocket will be assembled in space anyway, so not being subject to any meaningful gravitational nor accelerational stresses, we can easily build a 100000 or even 500000 ton rocket - basically just the reactors and tanks of acceleration mass - and thus get 100-500 ton payload. If we get any [semi]hybernation going (may be combined with 3d printing or CRISPR-like repair of organs, whatever we get in 20-30 years) or more probably some brain [partial] upload integrated with AI into some capable cyborg, may be even some people or those merged human/AI cyborgs would be able to go. And by collecting some additional reaction mass ram-style over that distance and time (as long as we have enough reactor power to use part of the collected mass to avoid slow down resulting from the collection) we'd probably be able to slow down some small probes to land and orbit various objects in the target star system.