Once you lose the ability to do things like pull weeds outside, can a person gain that strength back?

Absolutely you can regain strength. You will be amazed. No need to rush, though. Slow and steady at rebuilding. Jessie's walking suggestion is excellent. And, if you want pain free and fun exercise that will help you gain strength and flexibility? See if you have a local water aerobics class. Bestest there is!

Good luck!

It's great that you are feeling like resuming your activities. Since you are weaker than before though, I would make sure that someone was around the first couple of times in case you run into a difficulty. If that's not possible, make sure you let someone know you are going outside and when you will return inside to call them. I'd take my cell phone with me, in case you need assistance.

I would keep the time and level of activity down and increase it slowly as you regain your strength. Do you have a way that you can sit down in the yard if you start to feel weak? I'd just plan ahead.

Yes. You should start slow with short walks and moderate exercise, then build from there. I think everyone has periods of dormancy when the weather keeps us curled up inside with a good book.