First and foremost - DO NOT MEMORIZE! You need to UNDERSTAND the ideas and moves, not memorize them. Use a board and pieces, not a computer screen. Forcing to make the moves and resetting re-enforces more than clicking a mouse button. And I don't pick variations, I learn the opening as a whole.
Like in my case, that is the French Defense. To diversify the positions and not have it get stale, I play the Classical, McCutchen, Winawer, and Rubinstein. No reason to learn multiple openings. Learn multiple variations of one opening.
You cannot FORCE any opening. Both sides decide the opening, and your opponent makes half the moves.
I’m still very early in my learning career but find it hard where to even start with learning an opening. I like the Italian for simplicity and reinforcing solid opening principles. But I often get lost after move 3 and confuse all the different variations and ideas to build on. I sit through countless videos and lessons, try to apply it and just find myself overloaded and way behind in position everytime.