Yes, it is most effective that way.
Yes. Medicine in your system is like an alka seltzer tablet... lots of bubbles first and less at the end. Extended release versions try to even the bubbles for the referenced time. At the end of the referenced time the amount of medicine has waned enough that if the next dose is late you will not be maintaining a consistent level in your system. This is not only hard on a body, but effects the quality of treatment.
I do what Dr says & bottle of pills says. It's usually at same time. Unless it says PRN. Then you take when needed. Maxy