Will lifting heavier make me code faster?

I doubt it, but it's fun.

If you're lifting for strength a sedentary job helps. Lift heavy, eat heaps and rest plenty. You'll get very strong over a long period of time.

That is if your goals are purely lifting strength. The above method works for winning amateur lifting comps but leaves you with a bit of surplus fat and no cardio fitness.

The number of hours you extend your life by running is the number of hours you spent running. Apply a similar analysis here.

Probably not, but cardio and meditation might. Cardio will push more oxygen to your brain and may help develop brain cells.

https://selfhacked.com/blog/ways-increase-neurogenesis/

The only thing lifting will make you do is enjoy your life more. This may apply downward pressure on burnout, which will make you code longer. It probably will not help you code faster.