They can apply for a visitor visa, but it might be tough. The I-130 you filed shows immigration intent, and tourist visas are only for short stays with the expectation they’ll return home. U.S. consulates are strict about this

Yes, they can try to visit you while the green card is processing, but it’s not always easy. Since you’ve filed an I-130 for them, the U.S. government knows they have immigration plans, which can make getting a visitor visa harder

Yes, your sibling can apply for a B2 tourist visa to visit the U.S. while the green card petition is pending

Yes, your sibling can apply for a visitor visa, but approval isn’t guaranteed. They must prove strong ties to their home country and no intent to immigrate during the visit.