You can take a vegan diet right now, no problems at all.

Just focus on yourself, then convince one other person later down the line

At once? No. But via advocacy and trying to claw people to the side of veganism, even partially, over time industry adjusts.

absolutely, plants and vegetables have been around since the dawn of time, and once we stop funneling those plants through animals so they can grow fat and get slaughtered, we can just eat the plants directly from the source :) like @Cowbee said (no idea how to tag people on lemmy, sorry), however, getting everyone on board is a process

the only reason why animal meat is so rich in b12-vitamins is because it is artificially pumped with it. nutritionally the exact same as taking a supplement tablet, except the supplement tablet doesn't go through a gas chamber before they sell it to us

edit: here's a handy site that answers the most frequent arguments against veganism: https://yourveganfallacyis.com/en - i also recommend Ed Winters ("earthling ed" on youtube), i'm currently reading through the first of his two recent books on veganism