If I understand your question correctly, the train goes from A to B and from there to C. You are in A and buy a ticket. A is your "point of reservation".
The ticket you have purchased is good for the passage from your "point of embarkation" (B) to your destination (C). The ticket from B to C allows you to be transported by train from B to C. It does not give you the passage from A to B.
In other words: a ticket from a point of embarkation to a destination does not necessarily include the passage from the point of reservation to the point of embarkation. If you want to go from the reservation point (A) to the destination (C), you have to buy a ticket between these two points. Because the A-C distance is longer than the B-to-C, the A-C ticket will be more expensive.
Your first sentence is "If I board from my reservation point which is a station before my boarding point, will I be considered without a ticket between the booking and the boarding point. " Assuming that it's a question, the answer is "Yes, you will be considered to be without a ticket."