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.