shinkansen tickets and luggage

hi, my family and i will be travelling to tokyo on Dec 2023 then go to osaka by bullet train. I would like to ask the following questions :

1. where can i purchase the shinkansen tickets from tokyo to osaka?
2. which station in tokyo will the shinkansen leave for osaka?
3. which station in osaka will we arrive if we take the shinkansen?
4. How much is an economy class ticket for adult and/ or child?
5. How much is a business class ticket for an adult and/ or child?
6. Up to what age is a child's ticket?
7. if i purchase an economy class ticket,
   a.) where can we reserve space for our luggages ? b.) when are we allowed to reserve a space for our luggages? c.) How many luggage is/are allowed per person in an economy class ticket? d.) If it's one luggage per person, what will happen to the extra luggage if we have one? if we are going to get charged for extra luggage, how much is the cost?
8. if i purchase a business class ticket,
   a.) do we need to reserve space for our luggages ? b.) when are we allowed to reserve a space for our luggages? c.) How many luggages are allowed per person in a business class ticket? d.) If it's one luggage per person, what will happen to the extra luggage if we have one? if we are going to get charged for extra luggage, how much is the cost?

Thank you for helping me out in my queries.

Yours truly,
apan416