Some questions about EU4 trade? [closed]

I am new to EU4 (playing the demo right not) and I am confused about several things:

1) What determines how much money is kept in a node? Can this be changed?

2) Suppose my home port is A, which recieves trade from B, which recieves trade from C. If I send a merchant to C, will he know to transfer trade towards B? What if there are multiple indirect routes from C to A? Will he optimize automatically?

3) Does backflow of trade power work exactly as trade steering, or is there anything different about it? Suppose again that my capital is in A, but now trade flow from A to B to C. If I send back trade power from C to B but I don't have a merchant in B, is it completely useless?

4) If I have trade power in my non-capital node but I do not send any merchant to collect trade, do I get any money from that node?

Thank you.

I can answer 1,2 and 4, but am unsure about 3.

1) Money kept in the node is based on the relative trade power of all countries who have that node as their main trade node compared to all countries trying to steer the money elsewhere. You can decrease the money leaving your trade node by increasing your trade power.

2) If you send your merchant to C, he should optimize to send the trade value to the node that is the shortest distance to your home node, or else to the one that you have the highest trade value in. You can also manually set where the trade will go, but I personally have never needed to.

4) You do not get money from that node, and in fact I find that collecting money from any node except your capital node to be incredibly inefficient. It's much better to steer that money to your capital node, where it gets collected by the merchant you have there.

Hope this helps!