The first,I should pass with only 4 hcp.
then the second,after double,Gib N should rebid 1nt instead of 1♠,this is a GIB rebidding descriptive wrong.
How are there different between 1♠ and 1nt?
the meanings of rebidding 1♠ showed 5-4 or 4-4 distribution at least with low limited values, and usually it is a unbalanced hand.
the meanings of rebidding 1nt showed 18-19 hcp with balance,maybe have any 4 card major.
I think this is a basic bidding principle,what else?