It is difficult to say because these are unnatural sentences. For example, hy are you grateful because you made a cake? Maybe: I'm grateful to you for making the cake. I'm grateful for surviving the ten-year war. I'm grateful for ... being alive / existing at the same time as you? (Not sure what you want to express here.)

A: Both are OK. Left is more common & casual. Right is more posh & bookish. B: Both are poor grammar. I would omit "during", or replace it with "through", then both versions are fine. Left is more simplistic. Right is more specific. C: Both are technically OK but the meaning is a bit vague. Consider something like "I'm grateful for being alive in your lifetime" to remove any lack of clarity about what you're trying to say.