Will this hold my engine while I pull the transmission?

Yes. At 2000 pounds capacity, it handles most street and small-block engines with transmission still bolted on. Make sure your engine assembly doesn't exceed the rating — weigh it if you're borderline.

Does it lock in the upright position or do I need to bolt it down?

Stand is designed for stability on flat floors. If you're working on a slope or uneven surface, secure it to prevent tipping.

How much floor space does it take up when folded?

Folding design is meant for shop storage efficiency, though exact dimensions when collapsed aren't specified — test fit in your space before committing to permanent placement.