Yes I think it is just her current address. Petitioners have to show 5 yesr history.
Enter her name as it appears on her birth certificate and other government issued documents.
Same with her address.
Yes, upload copies of her birth certificate, marriage certificate (with your stepfather), proof that she was divorced or became a widow, your birth certificate, her passport, your passport, and any civil documents that pertain to you (marriage certificate or proof you were never married or proof of your divorce, if applicable)
yes, you have to include all children (regardless of their age) - as well as yourself to show your relationship to your biological parent and your siblings.