Is a routine necessary? Is it beneficial to have a consistent routine, a plan of exercises to be followed precisely each time I work out? Here's a couple choices, just give me the best answer.

Keep the same exact, steady routine...same exercises for each muscle and switch it up after a month or so.

Same routine, but switch it up after 2+ months.

Have two routines and do a specific routine for one cycle (back, arms, shoulders, chest, legs) then do the second routine exactly, for one cycle, and continue to alternate.

Don't worry about having a precise, steady routine, as long as your lifting weights. Just get to the gym and do the first 3 or 4 exercises you can think of for each respective muscle.