For the second question, Im assuming you asked about the Sales Ledger CONTROL ACCOUNT 

 instead of the Sales Ledger. Ok, so, the Sales Ledger Control Account (a.k.a Debtors Ledger Control Account) always starts off with a debit balance (as the people you sell goods to are the debtors). The format goes like this:
               Balances (Total of Debtors' balances)              A debit balance
               Balances (Debtors with credit balances)           A credit balance
               Credit Sales                                                A debit balance
               Sales Returns                                              A credit balance
               Cheques recieved from Debtors                       A credit balance
               Dishonoured cheques                                    A debit balance
               Overpayments refunded                                 A debit balance
               Discounts Allowed                                         A credit balance
               Bad Debts written off                                    A credit balance
               Interest Charged to Debtors on overdue Accounts  A debit balance (because this would INCREASE the amount the debtors owe)
               Transfers (set offs)                                      A credit balance
      I hope you understand these transactions; any confusion, ask. I'll move onto your third question. 
