5) It's ok to have bad workouts

Sometimes your training will feel harder than it normally does. That's ok, it happens to every lifter.

If you think you might need a change, look back at where you were 3+ months ago to decide if you are in a plateau.

4) It's ok to miss a workout

Life happens, and you aren't going to make every single workout. What's important is you don't give up and get back to regular training.

3) Train 2-4 times a week

You don't get stronger in the gym.

You get stronger recovering from the gym.

This is why rest days are not only fine but important to become a strong lifter.

2) Have a plan/program instead of random workouts

Random workouts are fun, but they aren't the best for building strength.

Having a plan makes easy to track progress and is going to be less work for more results in the long run.

1) Focus more on exercises that use multiple muscle groups at once

Squats, Deadlifts, Presses etc...

These exercises are better at building strength both in and out of the gym. Plus, it will take you less time than training each muscle group on its own.

3) Great exercises build strong lifters at any age.

Deadlifts, squats, rows—these exercises work whether you’re 25 or 45.

Which exercise you choose and why could be different, but there are no "exercises to only do in your 20's".

It is not too late to become a strong lifter, you've got this!