1) This technique is pretty interesting because I guess how the flames erupt into a pillar underneath the target. A limitation of this jutsu would be in order for it to be offensively useful one who had to position their flames to attack directly underneath the enemy's feet in order to burn them with the pillar. To defend against said jutsu it would be best to move around so the enemy cannot get a clear shot.
2) This jutsu is interesting because it provides a sort of barrier of flames around the user which could be used to defend against jutsu. Also, there are multiple ways one can use this jutsu which makes it pretty useful in the right situation. A limitation of this jutsu would be how the flames have to surround the user first and then have to be controlled to attack a target. This jutsu seems to cover a wide ground range if wanted so it would be useful escape to go into the air.
3) This jutsu is interesting because of the unique fire manipulation involved what I mean by that is how the user crafts their fire into a spider shape. A limitation of this jutus would be how it requires for the user to actually get the fire around a target in order to useful in battle. To defend against said jutsu you could attack the flames before they completely surround you and trap you.
In regards to the second technique you were on the right track on the defense but forgot to leave out how it also acts as an offense. So when you're fighting if you can in one move defend, interrupt, and attack then you will have immediately turned the tide of the battle into your favor. That is the advantage of techniques such as this.
In regards to the first technique yes it is interesting as it sort of influences how the opponent positions themselves. There is an audible tell to this technique as well to hint that it is going to happen to you. Because the moment it erupts and you are already standing on it, should you have not done anything to prevent it, you'll pretty much be guaranteed to take the damage.
These are the final B-Rank techniques.
( Katon: Hi no Iki ) - Fire Release: Fire Breath
Rank: B
Type: Offensive
Range: Short - Mid
Chakra Cost: 20
Damage points: 40
Description: The user breathes a powerful stream of fire from their mouth at their target.
( Katon: Honoo no Heki ) Fire Release: Flame Wall
Rank: B
Type: Offensive/Defensive
Range: Short
Chakra cost: 20
Damage points: 40
Description: The user kneads fire chakra into their forearm and then by swinging their arm in a wave motion they release the fire chakra creating a line of fire that spreads out infront of the user acting as a defensive wall.
( Katon: Hinotama no Mai ) - Fire Release: Fireball Dance
Rank: B
Type: Offensive
Range: Short
Chakra cost: 20
Damage points: 40
Description: The user will attack the opponent with a series of slashes with their sword and then finish up with jumping into the air above the target and releasing a powerful fireball down upon them.
Note: Requires a Sword.
( Katon: Yūgana Honoo ) - Fire Release: Graceful Flame
Rank: B
Type: Offensive
Range: Short
Chakra cost: 20
Damage points: 40
Description: The user manipulates their fire chakra and doing the tiger hand seal, shoots an intense fire stream at the opponents feet which then lifts them into the air in the eruption of a column of intense flames. Sasori can replicate this technique through the usage of his fire launcher.