You don’t need a backup plan.
Make a plan and focus on it.
If it needs to change, then it changes, but there is only one plan.
You only make a backup plan when you are afraid that your current one won’t work, and a backup plan is always limited by your current perspective.
Plus, it is never the best solution, or it wouldn’t be a backup.
It is a projection into the future based on the same limited information that you have now, and embellished by your mind’s conditioned survival fear response.
Why waste time on a second best plan based on fear?
Make the best plan you can, knowing that you can change it if you need to, and if you do, it will be from a new perspective, and with new information.
Then move confidently forward.