Why is Axiom $5$,in the list of Euclid's axioms,considered a 'universal truth'? (Note that the question is not about the fifth postulate.)

Consider two 'postulates' given below:
$(i)$ Given any two distinct points $A$ and $B$,there exists a third point $C$ which is in between $A$ and $B$.
$(ii)$ There exist at least three points that are not on the same line.
Do these postulates contain any undefined terms? Are these postulates consistent? Do they follow from Euclid's postulates? Explain.

Give a definition for parallel lines. Are there other terms that need to be defined first? What are they,and how might you define them?

Does Euclid's fifth postulate imply the existence of parallel lines? Explain.

Give a definition for the term 'line segment'. Are there other terms that need to be defined first? What are they,and how might you define them?

Give a definition for the radius of a circle. Are there other terms that need to be defined first? What are they,and how might you define them?