In the 3rd case, you can lose your initial $2k at expiration, but you will end up with 100 shares.
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In the 4th case, it doesn't cost anything, but you can lose up to $30k if SPY goes to 0 (very unlikely).
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In the 4th case, it doesn't cost anything, but you can lose up to $30k if SPY goes to 0 (very unlikely). More likely is SPY ends up lower at expiration than your trade price, and you pay that difference.
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As you can see, there are many ways to use your cash just with this one investment.
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These are worst case scenarios. If the market moves in your favor, the leveraged instruments will make you much more money than the 1st case. As you can see, there are many ways to use your cash just with this one investment.