[wildwood]

Hi Zephed,
On your first question: As long as the brokerage allows both orders. Certain situations can arise here. Suppose you bought stock at $10.00 ,entered a stop loss at $9.50 and a limit order at $11.00. Now let's say the stop dropped to your stop loss price and your stock was sold, then rose to your limit price before your limit order was cancelled. You could wind up selling stock you don't own. Not likely, but possible.
On your 2nd question, let's say you and 10 other people have limit orders to sell 100 shares each xyz stock at $15.00 That's a total of 1100 shares. Now let's say the market rises to $15.00 and trades 500 shares at that price and then reverses and falls back to $14.00. You can see that 600 shares will not get filled at the limit price unless the stock goes back up.