A "worker led" anything is possible. Look at how much fucking money private investors and executives remove from companies - companies are always far healthier when run by employee collectives and unions, while far less effective, still significantly improve long term prospects.
Twenty five year olds can have bad backs and your HR department knows your real age if anyone questions it (and you could always retroactively claim you were joking on your first day and thought everyone was in on the obvious deception).
Assuming it isn't an inherent job duty, ask not to lift heavy things and if someone objects then get a note from your doctor.
Nosey people can get fucked - we all have the freedom to choose what parts of our private life we share with coworkers and what we don't so you have no obligation to disclose your age (outside of anything relevant to payroll/taxes/insurance enrollment).
There is no need to change anything. Just don't let yourself be pressured into work you're not capable of doing. And if anyone questions your marital status or what-not... They're an asshole and can get fucked.
Edit to add:
After some discussion in the other thread, I think it's pretty regrettable to outright lie about your age - if you change jobs again, I'd really suggest just refusing to answer and deflecting the question. Telling such a direct lie likely makes some of your coworkers uncomfortable.
Don't worry! We couldn't kill all life on earth if we tried! We'll just kill all the humans and large animals... and we'll get to mulligan that in a few million years anyways.
You have the right to do your job in a safe and healthy environment. Other people don't have a right to make a workplace hostile by pushing their agenda. Just mention that you're not comfortable discussing religion or politics in the workplace and consider lodging a complaint in writing to HR in case you're suddenly let go "without cause".
Actually important NDAs do this - they'll just pay you to come in (or at least not work anywhere else) until the knowledge you had is irrelevant... and if the action that the NDA would prevent is legitimately damaging there do exist laws around corporate espionage that already cover these breeches. If you outright steal legitimately protected information from an employer (a common example is customer lists) and resell it... an NDA isn't needed. NDAs have traditionally just been used as a scare tactic to contain information that isn't legitimately protected... and, of course, to unfairly punish ex-employees for leaving.