1. As the first explanation was given, while focusing chakra down on the ground, only 2 m on his left, the young Uzumaki started effecting the earth with raw chakra causing it to simply break apart and move the way the tunes did. He did then constantly down, until the tunnel reached a depth of 2 m, then he continued the same principle with a lot of concentration moving the tunnel towards his sensei, while his vision was somewhere else entirely he simply wanted to find out, if his sensei would notice the vibration. Once the tunnel reached a distance of 14 m, he finished the jutsu considering it is enough proof that he had learned it.
How I will use the technique offensively
You said yourself, this jutsu has no offensive capabilities, but I am able to think of maybe something you could to with it. If you can continue the tunnel very close to the actual surface of earth and continue it till the enemy, then go once again, directly under him and dug quite a deep hole. You can further use earth attacks to break that thin layer of earth trapping your opponent or sending him a couple of earth spikes. I don't know if it can work, so correct me if I am wrong.
How I can defend against the tech
If the above statement is actually true the only way to defend against it, is to pay good attention to your enemy, if he is behaving suspiciously and always keep moving so you can't be trapped easily. If the above statement doesn't work, then you don;t need to defend against it since it can't harm you in any way.
Whether or not I find the technique useful or interesting
I have no special feelings towards this technique.
2. For the second jutsu, Nikodo didn't have all creations in his arsenal so he simply explained how it would work. The user will focus earth chakra in his body, slowly turning the molecules he has set up, into earth molecules, once that is complete, you simple create from your chakra a rock of compressed earth which will fire against your enemy. As you said this jutsu is pretty self explanatory, and not a good choice at all. If you want to throw a rock simply pick up one and throw it, you waste, no chakra, no time, and no moves.
How I will use the technique offensively
I would use this skill, to attack an enemy quickly when he is making seals, so that he will be forced to cancel the jutsu, but always if I have all creations pre-used. Another offensive usage might be attacking the enemy behind or on the side, aiming for a K.O from a hit to the head
How I can defend against the tech
There are millions of ways how to stop a flying rock towards you. You can, throw a kunai, shuriken, sword, another person, another rock, with great ease. Another way to defend against it is to simply move away from it's trajectory and even another way is to set up an earth wall...
Whether or not I find the technique useful or interesting
No useful, no interesting no nothing. I have no feelings for this jutsu of any form.
How I will use the technique offensively
You said yourself, this jutsu has no offensive capabilities, but I am able to think of maybe something you could to with it. If you can continue the tunnel very close to the actual surface of earth and continue it till the enemy, then go once again, directly under him and dug quite a deep hole. You can further use earth attacks to break that thin layer of earth trapping your opponent or sending him a couple of earth spikes. I don't know if it can work, so correct me if I am wrong.
How I can defend against the tech
If the above statement is actually true the only way to defend against it, is to pay good attention to your enemy, if he is behaving suspiciously and always keep moving so you can't be trapped easily. If the above statement doesn't work, then you don;t need to defend against it since it can't harm you in any way.
Whether or not I find the technique useful or interesting
I have no special feelings towards this technique.
2. For the second jutsu, Nikodo didn't have all creations in his arsenal so he simply explained how it would work. The user will focus earth chakra in his body, slowly turning the molecules he has set up, into earth molecules, once that is complete, you simple create from your chakra a rock of compressed earth which will fire against your enemy. As you said this jutsu is pretty self explanatory, and not a good choice at all. If you want to throw a rock simply pick up one and throw it, you waste, no chakra, no time, and no moves.
How I will use the technique offensively
I would use this skill, to attack an enemy quickly when he is making seals, so that he will be forced to cancel the jutsu, but always if I have all creations pre-used. Another offensive usage might be attacking the enemy behind or on the side, aiming for a K.O from a hit to the head
How I can defend against the tech
There are millions of ways how to stop a flying rock towards you. You can, throw a kunai, shuriken, sword, another person, another rock, with great ease. Another way to defend against it is to simply move away from it's trajectory and even another way is to set up an earth wall...
Whether or not I find the technique useful or interesting
No useful, no interesting no nothing. I have no feelings for this jutsu of any form.