Q1 Answer
1 SPADES
Your partner has doubled and you cannot pass as NORTH has passed. So bid your best suit giving preference to a major.
Q11 Answer
Q2 Answer
1 Club
You have 11 HCPs and 4 diamonds and 5 club cards. You can open under the rule of 20 (add the number of cards in 2 longest suits to HCP total and if >20 you can open). Clubs is your longest minor and you have no 5 card major, so open 1 Clubs.
Q12 Answer
1 NO TRUMPS
As NORTH has passed and you have 9-11 HCPs, no 4 card major and a stopper in SOUTH's suit you should bid 1NT after your partner has DOUBLED.
Q3 Answer
2 No Trumps
Your partner has overcalled and should have > 10 HCPs, 2 of top 3 honors in spades. You have stoppers in hearts and 13 points. This is enough to invite partner to game in 2 no trumps.
Q13 Answer
2 DIAMONDS
You have 10+HCPs your partner assumes that you have 4 hearts after their 1C bid. To tell them that you have 5 hearts you 'lie in a minor' by bidding 2D.