Yes, unlocking a router you own is legal in most countries for personal use.

Firmware unlocking is the process of removing the restrictions imposed by the manufacturer on the router's firmware, allowing users to modify, customize, and extend the functionality of their device. This process involves replacing the original firmware with a custom or unlocked version, which can provide advanced features, improved performance, and increased security.

No. Unlocking only removes SIM restrictions. Speed depends on signal quality, carrier, and congestion.