Hello. Welcome to Carcassonne Central
Now to answer your questions:
1) Yes. A tower foundation ends a road. Example:
there are two roads here, seperated by the tower foundation.
OR
You might be referring to a cloister, in which case the same is true:
there are two roads here, seperated by a cloister.
2) I think I know what you mean here. If you mean like this:
then they are not connected and a follower can indeed be placed on both of them.
The same is true of this example:
these are also not connected... yet! (and they might never be, if the right tile comes up!)
3) Yes, by not placing a follower in that city.
4) Yes, the river also acts as a boundary for farms as do roads and city walls. BUT... in the basic River tiles the farm continues around the spring and also around the lake.
5) As above. Yes it can (The source of the river is also known as the spring)
Spring Lake
farms continue around both of these features.
I hope that answers your questions. If you require any more help, just post a message and someone will answer any queries you might have. Enjoy your Carcassonne games and Carcassonne Central