Safe-Life: This is de minimum life during which it is known that no catastrophic damage should occur. The life of such a structure can be defined in different ways, cycles, flight hours, pressurization events or calendar time. After this interval has been reached the structure should be replaced, inspected or overhauled per manufacturers recommendations.

“Multiple load path” and “Damage-tolerant structure” both refers to a fail-safe system:
Fail-safe: When a structure fails there is alternative load-path provided by an adjacent part which is able to take over the loads for a limited amount of time. This normally should be enough time until the next periodic inspection where the damage should be identified and the damaged part replaced.

Redundancy means that there are more than one systems which can do the same task in case one or more fail. That’s why modern aircraft usually have 2 or even 3 hydraulic systems which can take over the functions of the other in case it fails.