Can invisalign braces straighten adult crooked and crowded teeth?

Maybe. depends on the level of crowding. I would discuss with an orthodontist.
To some extent. Very mild crowding or spacing can be addressed with clear aligners (they are not braces). They are less than half as effective as braces, cost more, and in the hands of a trained orthodontist usually require more time in rx than braces. The place where most gp's, who do aligner rx, call it quits make orthodontists cringe. Why not go for an exam to find out your options.
Questionable. After 30 years of practice I am not an advocate of invisalign. The results are less than ideal and long term stability is not there. I do not use invisalign in my practice. It is a great practice builder, but I do not think it is in the patient's best interest. I'd rather do nothing.
Perhaps. Invisalign technique is good but it has its limits and may not be used. Keep in mind that method is about 20-30% costlier. Ad you might still need brackets at the end to fine tune. I finally got brackets (plain old metal) when i was 50. My patients thought it was neat. And nowadays..People will look at you and know you are "taking care of yourself". See a dentist that does invisalign.
Yes. In most instances. See an orthodontist for a consultation.
Yes. Invisalign takes longer than convention braces since the forces are not applied continuously. Also, there can be tracking issues. That said, new features of invisalign allow incredible results that rival wires and brackets. It is not just for minor corrections anymore. Correct diagnosis is always the primary ingredient for a successful outcome by general dentists and orthodontists alike.
Absolutely. Clear aligner treatment is often applicable to adults with crowded teeth; however, the only way to determine if it's right for you is to seek an individual evaluation of your needs by an orthodontic specialist.