Could be false. We don't have any statements that establish when something is returnable for a refund. We know that sale items are not returnable for a refund, but this doesn't establish when an item is returnable for a refund.

Could be false. We don't have any statements that establish when something is not returnable for credit. We know that sale items are returnable for credit. But this doesn't establish that non-sale items are not returnable for cerdit.

Could be false. We know from our conditions that some construction tools can be returned for store credit, but this does not imply that there are some tools that cannot be returned for store credit. The quantifier “some” means at least one. So it's possible anywhere from one to all construction tools can be returned for store credit. Also, although we know that "selected" tools are on sale, which arguably implies that there are some tools that are not on sale, this doesn't imply that the tools that are not on sale cannot be returned for store credit.

Must be true. As shown below, we can chain our conditional claims and see that any piece of gardening equipment cannot be returned for a refund.

Could be false. We know from our conditions that some construction tools are not returnable for a refund, but this does not imply that nothing returnable for a refund is a construction tool. We cannot take the contrapositive of a “some” statement. It's possible that there are some construction tools that are returnable for a refund (as long as these tools are not the ones that are on sale).