yes is it possible to do a 1 class build from fresh start to end game with just found gear?
Do you mean one mastery? Yes, but you’re gimping yourself for stats since you won’t get those boosts from a second mastery bar.
What medea said. They’ve been doable as far back as vanilla but I’d only recommend them if you have a good amount of game experience/knowledge or follow guides on it by those that do, e.g. @Maya has milestones for levelling solo Necromancer and Occultist with pets in her Carnival guide.