Question

Could only and other be an alliteration?

Answer 1

Yes, if they are put word by word like the example below

There could be only one other way to figure out the puzzle.

A coomon known alliteration is Peter Piper Picked a Peck of Pickled Peppers.

Do you see a pattern?

Answer 2

No, they don't have the same sound. And alliteration is usually the repetition of consonants, not vowels.

"rifles' rapid rattle" (from a poem by Wilfred Owen, for example)

(In "only" the "o" is a long vowel. In "other" the "o" is a short vowel.)