I'm a self-confessed train nerd, but there remain large gaps in my knowledge, mostly concerning how the railways of the past actually operated on a daily basis. I could tell you all sorts of things about closed lines, old stations, which companies ran trains in which areas, who designed what locomotives, but I've genuinely no idea how the railway itself operated, especially from the point of view of the passenger/customer.
Let's assume it's the 1930s somewhere in England, and I'm a wealthy businessman. I live in town A and I own a small factory in town B. I make regular deliveries to towns A, B, C, and D.
I realise this may be a tall order, and I apologise if I've broken any rules of the sub, but I'm grateful for any help you can offer.
Assuming your hypothetical factory is not connected to the railway with its own siding, then raw materials would be delivered by rail to a goods yard in the town. Every town had hauliers/carters who would deliver the materials to your factory from the goods yard. In a larger town the Railway company would also have their own hauliers. You would decide which to use depending on price.
By the 1930s rail freight in the uk more or less acted as a single system with freight moving between the companies quite efficiently. Cost was allocated between the companies based on mileage through the Railway Clearing House. So transporting a load of widgets from a goods yard on the LNER to one on the Southern was seemless from the customers point of view. You would be billed by the LNER and the income would be divided among the companies depending on mileage.
To organise a special train to the seaside you would contract directly its the company. In a small town the Station Master would handle your request and liaise with the parts of the company involved to organise rolling stock, timetabling, and most importantly billling. How much it would cost would depend on where you were going from and to. But these were not uncommon requests and every weekend in summer would see dozens of such special trains.
I can't help with your other questions as they are too vague to say anything meaningful, but, if you want to specify some places I could give some details.