IoT devices often generate diverse data types, including structured, semi-structured, and unstructured data. NoSQL databases are a suitable choice because they can handle various data types, provide flexibility, and scale horizontally to accommodate the growing data from wearable devices.

Requiring both a password and a biometric scan is a form of Two-Factor Authentication (2FA). It adds an extra layer of security beyond a simple password, making it harder for unauthorized users to gain access.

The integration of 5G technology in IoT can substantially improve interoperability, ensuring that various IoT devices can communicate effectively and efficiently. This is a challenge that 5G addresses in the IoT landscape.

C++ is often considered the most suitable language for real-time IoT applications due to its efficiency and low-level control over hardware. It allows for precise resource management, which is crucial for real-time systems. While Python, Java, and Ruby have their merits, they may not be as well-suited for real-time IoT.

The process of ensuring that an IoT device operates within its intended purpose and network is called "Device lifecycle management." It involves activities like provisioning, configuration, monitoring, and maintenance to keep the device functioning as expected.

As the number of IoT devices grows, ensuring data integrity and quick retrieval is crucial. Security measures become critical to protect the data from various threats and vulnerabilities.

Advanced visualization tools in IoT are crucial for gaining insights from complex data. With the enormous volume of data generated by IoT devices, visualizations help in presenting the data in a comprehensible manner. This is vital for analyzing trends, anomalies, and making informed decisions in IoT applications.

Blockchain enhances IoT security through data immutability. Blockchain's distributed ledger ensures that once data is recorded, it cannot be altered, making it ideal for securing the integrity of IoT data, such as sensor readings and device logs.

Devices connected via the Thread wireless protocol are known for their ability to create self-healing mesh networks and connect directly with one another. Thread allows devices to communicate in a decentralized manner, eliminating the need for a central hub or router.

Requiring unique digital certificates for each device emphasizes Identity and Authentication. It ensures that each device is who it claims to be, adding a layer of security to prevent unauthorized access or data breaches.