[Asterisk-Users] How "real time" is realtime?

[Asterisk Supporter]

How "real time" is realtime?  If the extensions.conf is stored in the
database, does * query it row by row or is it "cached"?  In other words,
given the following exerpt:

exten => 5001,1,Dial(IAX2/test at test/s,30,g)
exten => 5001,2,Voicemail(u5001)
exten => 5001,102,Voicemail(b5001)
exten => 5001,103,Hangup

exten => 5002,1,Dial(IAX2/test2 at test2/s,30)
exten => 5002,2,Voicemail(u5002)
exten => 5002,102,Voicemail(b5002)
exten => 5002,103,Hangup


If 5001 received a call at 5001,1 and was answered can row 5001,2 be
replaced with:

exten => 5001,2,Goto(5002,1)

Overlooking syntax and typos in the dial plan, on the extension 5001
hangup ("g "attribute) will the caller be "transferred" to voicemail or
extension 5002?  Can I alter the dialplan in "realtime" as long as the row
has not been processed?