If prior retinal tear, risk at 60 of developing a retinal detachment or a posterior vitreous detachment?

See a retina special. You do have a somewhat increased risk of developing a retinal detachment if you've had a retinal tear (even if it was treated), though you should speak to your retina specialist to gauge your true risk based on your exam. Everyone develops posterior vitreous detachments as we age - that is regardless of having had a tear or not.
Could happen. Something about your eye led to a retinal tear at a youngish age. This could still be at play although presumably your tear was fixed with laser or surgery. The risk even at that is not too high, just a little higher than the average person. You should talk with your retinal surgeon about any special risks you have due to the character of your eye.