So once a tuple is created with some values can it be extended?

Answer 1

No, it can't be changed at all.

Answer 2

How about going around the problem like this... a bit unorthodox maybe!

tup1=1,2,3
tup2=4,5,6
tup1+=tup2 # would concatenate tup1 & tup2 in new 'extended' tup1

:)