could this forum help in A1 test preparations
Yes. I think Duolingo courses are more than enough for A1 tests, you could even get a A2. I have an A2 in italian and it's not more than what duolingo teaches.
I think that it will help with learning vocabulary. However, I think that the tests often have a big verbal component as well as reading comprehension, so you'd need to work on those more outside of Duolingo.