Can I say: 1.my finite vocabulary is benefited from reading.
2.I have no such an apprehension that it won't work.
1. This is just fine
2. Too many negatives. If you are not apprehensive about failure, say just that.
It is possible to use multiple negatives in the same sentence, but your writing will usually be more clear if you avoid doing it.
It is not impossible to use multiple negatives in the same sentence, but your writing will not be more unclear if you don't fail to avoid doing it.