?
Yes, past present and future
Bill-M
Yes.
Athena
Not "all the time," but often.
Morningfox
Yes, sort of. The process of a star "turning on" is a very slow process in human terms, many hundreds or even thousands of years. It's not like they just suddenly turn on. At the same time, there are other stars going dim. So the overall about of star light from any patch of sky is pretty much the same all the time, unless there is a supernova.
quantumclaustrophobe
It can be thought of that way. Like the nebulae around us that are producing new stars, there are those in galaxies far off likewise producing new stars. And, there are also stars that are 'dying' as well - supernovae that flash bright, then fade over time.