(While being || Being) a good person, he (devoured || had been devouring) kittens.
In this sentence I mean that he was always a good person in the past, not only while devouring kittens.
(While using || When using || Using) the services, (you agree || you're agreeing) to our terms.
I have seen every of above variants in real agreements as well as "by using ..., you're agreeing". What the difference?
We follow these rules (while providing || providing) the services.
That means that "we" follow these rules throughout the time we provide the services. Also, is it correct to say "during providing"?
(While being || Being) the main instrument for resolving such issues, this law must be applied.
So, this law has always been the main instrument for resolving such issues since it entered into force, it is not only for a period of time.