How is Mobile Studio administered in Marketing Cloud? What are the differences between short codes, long codes, and toll-free numbers?

MobileConnect (SMS/MMS):
— Short codes: 5–6 digit numbers (e.g., 12345) used for high-volume SMS marketing. Pre-approved by carriers, highest throughput (up to 100 SMS/second), requires carrier approval process (6–12 weeks). Best for promotions and marketing campaigns.
— Long codes (10DLC): Standard 10-digit phone numbers registered with The Campaign Registry (TCR) for A2P (Application-to-Person) messaging. Lower throughput, lower cost, suitable for transactional and conversational messaging. Requires brand and campaign registration.
— Toll-free numbers: 1-800 style numbers that can send SMS. Mid-range throughput. Require verification. Suitable for transactional messages and moderate-volume marketing.
MobilePush (push notifications): Requires configuring an app in MobilePush with:
— iOS: APNs (Apple Push Notification service) certificate or key
— Android: FCM (Firebase Cloud Messaging) server key
Contact-level opt-in/opt-out is managed per device registration, not per subscriber key, since a subscriber can have multiple devices.