When should I deload?
Listen to your body. There is no need to randomly deload every 4th week. If you start to feel beat up or fatigued take an off week or deload week after the end of your next 3 week cycle.
Even if you don’t feel beat up, consider taking a light week after 9-12 weeks just to do something fun, refresh your motivation and heal up a bit.
Can I swap exercise “X” for exercise “Y”?
Yes, as long as it’s a similar exercise variation. For example, you could use dumbbell rows instead or barbell rows, or standing curls instead of seated curls.
Can I add in traps, forearm or whatever work?
You can, but don’t go overboard. This program is well rounded as it stands.