People said the same thing about reusable rockets only a decade ago. Now they're common place.

All the things above are fully realizable in the coming decades, they are not in the realm of science fiction what so ever they are merely engineering problems.

1. Define “reasonable amount of time”

2. Define “technology”

The meta-technology of R&D and socio-economic programs that will make these things happen exists and gets better every day. If a method to perform the needful does not exist, it will given the right conditions.

Again, that is simply not true. The technology already exists. Need a modest rocket that can bring a nuclear reactor to an asteroid and heat up part of its mass as exhaust for a long enough time to deflect it by couple cm/s to maybe 1 m/s.

The only thing you need to do is to be patient. A lot depends on how greedy you are, if you want a smaller one it gets exponentially easier.

Just read this 10 year old report: https://space.nss.org/technologies-for-asteroid-capture-into...

Did you read the "Note" at the top of that link? From that it's clear that this is a many-decade project: if it had been started in 2011, it would only be partially done by 2030. That would not be the "reasonable amount of time" requested by parent. Technology will improve, and eventually all sorts of things will be feasible. More reasonable plans can be hatched at that time.

There is huge difference between multi-decade projects and "pure sci-fi" or "impossible".

"Reasonable" is subjective to define, but there are many multi-decade projects running right now so I don't think of multi-decade projects as unreasonable.

Things like sending man to the Moon or building Space Station would have been deemed "pure sci-fi" with the approach of the parent commenter.