Any economic policy that changes prices can be seen as inflationary if you pick the right index. The CPI is not what matters. What matters (to workers) is the ratio of the CPI to wages. It doesn't matter if the CPI rises (temporarily) as long as wages rise faster. As long as you are not actually just printing new money, the system will eventually reach a new equilibrium where workers have more bargaining power than they do today and capital holders have less. That is an attainable policy goal. The problem is that that the moment capital has all the bargaining power, and capital wants low wages, so that's what we have. As I pointed out earlier, this is great if you're buying, not if you're selling.
Since UBI isn’t likely to drive wages up (and, if as often proposed it replaces or offsets minimum wage, it may drive them down at the low end), I don’t see any real difference there, even if it was correct (I agree that what matters to workers qua workers is real [that is, CPI-adjusted] wages, and to consumers qua consumers real income; but that doesn’t alter the definition of inflation, just notes the inflation per se is not the concern for those groups in those roles.)
UBI is likely to lead to inflation, is unlikely to lead to general real wage increases (though that’s complicated), but will lead to real income increases in the low end of the distribution unless cranked too high high too fast (and there are negative feedback controls that should avoid that problem unless deliberately subverted, say by indexing UBI to inflation.)
That is far from clear. If workers don't have to worry about ending up destitute if they lose their job they will have more bargaining power. They would also be able to allocate more resources towards acquiring new skills.
One of the reasons workers put up with shitty working conditions is that the alternative, more often than not, is to end up on the street. Remove that from the equation -- by whatever means -- and lots of things will change.
Yes, you will (unless you do a flat capitation so thst everyone’s taxes are equal to their benefits, but what’s the point of that?) Downward redistribution is inflationary (in CPI terms) because of differences in the marginal propensity to spend, in the same way that upward concentration creates asset price inflation because of marginal propensity to invest.