The Vs Seeker was disabled as it was breaking LC. That is not likely to change, so no, there isn't and probably never will be, a working VS Seeker in LC.

Given time - there may be a suitable replacement put in however.

Not sure as i haven't played it recently, if there isn't, it may not happen unless LaZ decides to, and no one knows, including LaZ as hacks are not like budget based games. there is no time frame set, and most hackers despise such questions.

Though IIRC on a really old beta, i did get a coupple of rematch calls on my pokegear, though i could simply be confusing it with HGSS or even GSC