For question #1, you can combine the DONE outputs using any, but it may not do what you want it to. In your example, you poll 3 buttons using loop for each. I don’t think there is any guarantee that all three buttons will get checked before something after the any node executes. In this case, we are talking about someone manually pressing a button; unless you have a huge program (or some delay timers), program execution will be fast enough it would probably never be an issue. This will not always be the case; especially if the different paths have different complexities (i.e. 1 path checking button press, another performing a long path of multiple nodes doing calculations).
There is another thread where I provided example code using flip-flop to create a patch much like any, except the output doesn’t pulse until ALL inputs have pulsed (actually output changes to TRUE when all flip-flops are TRUE, which can be used as a pulse). Combining DONE Pulses Into a Single Output