I'm going to link a previous answer I gave to this question first which mainly addresses why the UK most likely never seriously considered giving Hong Kong to the ROC:

https://www.reddit.com/r/AskHistorians/comments/lu42hb/comment/gp7o41i/?utm_source=share&utm_medium=web2x&context=3

The last part of your question about ROC opposition is also interesting (and much more in my wheelhouse), so I'd like to add a little extra context. The ROC government at the time of the handover did not make a strong effort to oppose Hong Kong's recursion to the PRC. Despite the fact that tensions were high in cross-strait relations following the 1994 third Taiwan Strait Crises, the result of the handover in the short-term was little direct change in the Status Quo arrangement for both ROC-PRC and Hong Kong - Taiwan relations.

The scholarship I'm familiar with on the subject (see Chu's article below) makes the case that ROC policymakers came to the conclusion that they would have little to gain from actively opposing the handover. During the same period as the actual handover process was occurring, Taiwan was also conducting its first direct presidential election (1996) and revising its constitution, so domestic politics were a larger focus. Given these facts, the ROC government determined that a cooperative approach to redefining relations post-handover would be more beneficial to Taiwan than opposition.

I hope that provides a good overview of the context in which the ROC engaged with the handover at the time. I highly recommend reading the article below if you'd like more context there. I'm unable to find a non-paywalled version atm, but you may have more success than I do with diligent searching.

Chu, Yun-han. “The Challenge of the 1997 Hong Kong Handover for Taiwan.” Pacific Affairs 72, no. 4 (1999): 553–69. https://doi.org/10.2307/2672397.