Is there a real difference between:

1 It is worth buying this phone. – 2 This phone is worth buying.

I heard an opinion tat 1 is wrong. However, this is what I found in a dictionary.

3 It's worth discussing.

So, technically 1 is correct. Is there a semantic-related reason or something else that makes 1 incorrect?

On top of that, what’s the difference between.

4 It's worth discussing.

5 It's worthwhile discussing.

Is there a real difference between:

1 It is worth buying this phone. – 2 This phone is worth buying.

I heard an opinion that 1 is wrong. However, this is what I found in a dictionary.

3 It's worth discussing.

So, technically 1 is correct. Is there a semantic-related reason or something else that makes 1 incorrect?

On top of that, what’s the difference between.

4 It's worth discussing.

5 It's worthwhile discussing.