～てこそOnly if, Because, By, Unless, Until

Both use the emphatic こそ but differ by verb form. ～ばこそ is conditional, meaning only if (A), then (B), as in 忙しければこそ 'precisely because you're busy'. ～てこそ focuses on completion, meaning only after (A) happens, then (B), as in 苦労してこそ成功がある ('Only after hardship comes success'). ～ばこそ can introduce a hypothetical condition, while ～てこそ emphasizes the actual realization of (A).

These are both emphatic expressions that can be used in similar contexts to express 'it's entirely because of (A) that (B)'. あっての is narrower in use, saying that something was possible only because something else 'exists', e.g. 皆さんの努力あっての成功だ ('This success is entirely because of everyone's effort.'). てこそ can be used with a wider variety of verbs, such as 留学してこそ学べること ('things you can only learn by studying abroad'.).

Both からこそ and ～てこそ emphasize cause and effect, but they differ in nuance. からこそ highlights a specific reason with a strong emphasis, e.g. 努力したからこそ合格できた ('I was able to pass precisely because I worked hard'). In contrast, ～てこそ indicates that only after a certain condition is fulfilled can something else happen, e.g. 努力してこそ意味がある ('It only has meaning after putting in effort').

Both involve the same こそ, but one attaches to nouns and the other to verb + て form. こそ emphasizes a specific word or element, often to contrast or highlight, e.g. 彼こそできる ('He, if nobody else, can do it.'). In contrast, ～てこそ focuses a condition that must be met for something to be true, e.g. 大人になってこそ分かる 'understand only after becoming an adult'.