That's not the case in the US. There is no federal tax break in the US for "R&D" as far as I'm aware. Companies can deduct all expenses from their income. So there isn't even really a need for a tax break here. All salaries, rent, operational expenses are deducted from the income.

Moreover, many US corporations are effectively encouraged by tax law to go into debt (and always operated under debt), because having a zero effective income means you pay zero taxes. So that's what many companies -- they spend a little bit (or sometime a lot) more than their revenue, and thus report a loss each year (consequently paying zero taxes).

Yes, if you work in a large US company, they will tell you explicitly that they want to categorize as much work as possible as "research", for tax reasons. You may have to fill out questionnaires asking whether your work might fit any of a series of definitions of "research".

There's nothing secret about it.

Interestingly, the time is also classified by the ‘class’ of research, where class one research involve very basic improvements (like changing the speed at which you make something) that have a different tax bracket than class five research, which is closer to basic/applied research with no clear application in sight.