1) You do not "call a timer" — a timer calls you.
2) Timers should be best avoided; in most cases, a timer can be replaced with much more simple, robust and safe thread. Here is the explanation:
Timer Threading in C#[
^].
3) There are three types of timer in .NET.
System.Windows.Forms.Timer
(you probably mean in the question) is the worst one. It's probably designed for very inexperienced developers who do not demand any accuracy. If any timer should be avoided, but this type should be avoided by any means.
4) As to the questions Q1 and Q2, I agree with Cristian.
—SA