When can I play golf, ride a bike, or go hiking after spine surgery?

Wait long for golf. There is a huge range of types of spine surgeries. Minimally invasive disc or decompression patients, shouldn't engage in lifting of greater than 30 pounds for six weeks and to refrain from painful activities. Recovery from open fusions can take much longer. Hiking or bike- riding can usually be started relatively early in the process-2 or three weeks out. Golf needs to wait 6 months.
Soon. 1-6 weeks depending on the type of surgery and how you feel. The more you move the faster you recover.
Depends. Depends on the limitations from your surgeon. Should be a plan based on your level of function and pain. You should be recovered enough that you do things safely and effectively without risk of injuring yourself again. The sequence is less physically demanding activities first, walking in the pool b4 walking in neighborhood b4 hiking, stationary bike till comfortable. Golf will take longer.