Can you spell 'ein kind' as 'eine kind'?
yes, but it is incorrect.
das Kind
ein Kind
no "eine" allowed. And, since Kind is a noun, it is always capitalized.
Now, with adjectives, following a definite article, they are all ending in e. Otherwise, they are inflected by gender:
das kleine Kind
ein kleines Kind
Of course, there are other changes, depending on case...