First of all, thanks to all.
Learned remembers, I am just a hobbyist, I do not know much about electronics. I am here to learn, I hope you will consider this and will overlook my mistakes.
I am very much interested in High Voltage Projects which produces sparks, I have built some circuits. They worked fine. So I decided to learn more about their workings. I came across things which I did not know.
Since I could not find answers on google, hence I am asking here.
@treez what is the difference between staunch and and resonance capacitor, are they same? Some where I read that it is resonance capacitor.
@FvM schematic is theoretical schematic, many circuits seems to use use c1 and c2. I know they act as snubber, but I do not know when to use them and when not to.
I have asked in my question what is the function of c3?
LTSPICE schematic one is just a theoretical circuit with all possible components which can be employed.
I used that schematic to ask the question when to use a component and when not to and how to calculate their value.
I have included some circuits for consideration , please have a look.
in the schematic one a capacitor is placed between ground and base. I do not know the use of this capacitor nor do I know how to calculate it.
A diode and a capacitor is placed in between ground and collector, I know they act as snubber, but I do not know how to calculate the value of capacitor.
In Schematic 2, a diode is placed in between base and ground, what is the function that diode ?
In schematic 3 a capacitor is place across transformer, I do not know what is proper term for this capacitor, resonant capacitor , or snubber capacitor or something else or how to calculate it.
Flyback circuits use RCD snubber in general to mitigate the problems created by parasitic capacitance and leakage inductance.
Schematic 4, is the complete schematic that I have used after cropping in my question before.