GNURadio reconfiguring flowgraphs

Hello,

I'm interested in reconfiguring the flowgraph of my app at runtime.

I see that there is a set of functions to do that: start/stop, lock/unlock, connect/disconnect

https://www.gnuradio.org/doc/doxygen/page_operating_fg.html 

I have 2 questions about this:

1- Is it possible to use these functions in an hiearchical block or just only at top_block level?

2- What type of conditions to use to reconfigure a flowgraph? the only example given is time condition "time.sleep(0.01)". 

Thanks.

Best Regards,