Do these sunglasses actually block UV?

The lenses are labeled UV400, which means they are rated to block 100% of UVA and UVB rays. That is the same protection claim major brands make, though the plastic lenses are not optical-grade.

No. Nothing in the product indicates polarization, so glare off water and roads will not be reduced the way it is with polarized lenses.

What are the lenses and frames made of?

Both are ABS-PMMA plastic. That keeps them light and cheap but means they scratch more easily than polycarbonate or glass lenses.

Are they good for everyday wear?

They work as a spare pair or for short outings, but the plastic build and lens quality are not meant for daily long-term use. Most buyers treat them as disposable or event sunglasses.

Can I hand them out at a party or event?

Yes. The tie-dye finish and low per-pair cost suit giveaways, favors and group photos. Check quantities with the seller before ordering for a large event.