This was a fun little experiment my daughter did to test the usefulness of opposable thumbs. Here she is folding laundry. We used masking tape to keep the thumbs immobile, but it was a bit painful to get off so I don't think I'd recommend it.
Putting on the bottle lid was the hardest. Granted, this particular bottle has issues and it's difficult to perform this task even with thumbs.
She concluded that thumbs aren't necessary for many tasks, but they are sure useful and she wouldn't want to do without them. I love being related to monkeys. I'm talking about other primates, not my kids, by the way.