I have a few naive questions on the algebraic K-theory spectrum construction, but whose answers I couldn't figure out using the internet. I'm mostly interested in the case of a commutative ring, but I guess most of these questions apply somewhat more generally as well - e.g. $E_{\infty}$ ring spectra, or maybe more abstractly for something like exact monoidal categories.

1) I've seen several ways to construct the cup product in algebraic K-theory, which generally result in something on the level of the K-space, i.e. a map $K\wedge K\to K$ which is associative, commutative up to homotopy and distributive over the H-space structure up to homotopy. Am I correct that this also implies the corresponding connective spectrum is a ring spectrum?

2) Under what circumstances do the above structures lift to $\mathbb{E}_\infty$-ring structures? I would guess if you had similar coherence structures already on the symmetric monoidal category (so in particular all $R$-module categories since they're strict), but I am hopeless with all of that. Also, I don't understand the issues surrounding $E_\infty$-structures; it seems like this sometimes depends in what category of spectra you're working in.

3) In Weibel's K-book pg 79, a non-connective version of the K-theory spectrum due to Bass is given, basically by homotopizing the fundamental exact sequence. Do the structures (ring, $E_{\infty}$) from the previous questions extend here? (Also, as a digression, this construction seemingly only applies for rings - is there a version of this construct whose input is more categorical?)

4) (a bit more farfetched) For the kinds of rings you find in arithmetic geometry (esp. rings of integers in global fields), is there any relationship between the Bass non-connective spectrum and $K(1)$-localization? cf. the Lichtenbaum-Quillen conjectures implying that such rings are essentially $K(1)$-local.