1. Does the method guarantee finding the target?

Random Method:
No, the random method does not guarantee that the target will be found. Since the selection is random, there's always a chance the correct key may never be hit, even after billions of attempts.

Sequential Method:
Yes, the sequential method does guarantee that the target will be found—eventually. It walks through the entire keyspace in a defined order, ensuring the target is reached if it exists within the range.

2. Memory usage and performance

Random Method:
One major downfall of the random method is that you need to store every point that has already been calculated.
Why? Because there's a high chance the algorithm will hit the same key multiple times.
To avoid repeating calculations, you’d need to store and check against all previously visited keys, which requires a huge amount of memory.
This not only slows down performance due to frequent memory lookups but also increases the complexity of the implementation.

Sequential Method:
In contrast, with the sequential method, you don’t need to store every key.
You only need to track the last key calculated. There's no duplication, and memory usage remains minimal.
This makes the sequential method faster, more memory-efficient, and easier to manage.

Conclusion
While the random method might give the illusion of better performance in short experiments due to lucky hits, it comes with significant drawbacks: lack of guarantee, heavy memory use, and slower performance over time. The sequential method is predictable, memory-efficient, and guaranteed to succeed, making it a more reliable and scalable solution in the long run.