Here is a skill that many of us are going to need for survival: how to tell if someone is offering to let you lie.
The tip-off phrase is "If [circumstance] was true, then we/I could do [helpful thing.]" This is not a guarantee that the person is offering, but it should tell you "I am being informed of a way to improve things."
Your confirmation phrase is "What documentation would that require?" This is essentially asking them "if people come asking me to prove this, will I be able to? Or will they not come at all?"
The answer you are hoping for with the confirmation phrase is "Just tell me if it's true, and I'll put it on the form." Note that this is not a direct instruction to lie, because they can't tell you that.
If they didn't mean to extend an offer to lie or this is a situation where they can't, then they'll list off something like your paystubs or your birth certificate. Your response back in that case is "Thanks, I'll tell my friends who qualify." This clears you of any concerns that you may have been considering lying.
The more complex answer is when they answer by giving you a form on the spot. Your job, in this case, is to scan the form and see if what they are asking you can be meaningfully verified by an official source.
Things that can be verified by an official source include, but are not limited to, your age, legal sex, income, veteran status, and place of residence. It's not generally a good idea to lie about these on official documents.
Be smart, and be practical. Do what you need to in order to stay alive, and keep an ear out for the people offering to help you do so.