There are guitar amp simulators for the iPhone.  I don't remember if iRig is one of those or if it's for recording.  But yes you can do that.

Age 57 here and been playing about a year and a half.
I've had about 14 or 15 months of lessons between two instructors.

I ignorantly did not put importance on how high the strings were on my guitars(poor set up) and played with a lot of downward pressure at the finger tips from frustration and trying to make chord changes to fast. Apparently that put a lot of pressure on the joints.
Several joints in my fingers hurt most of the time and no longer operate smoothly. Hope I'm not causing arthritis and tendonitis.
Just recently heard the phrase "it's not about power it's about precision" and that makes sense to me now regarding fretting.

I don't practice for very long and take frequent breaks but continue to practice.
I had all my guitars set up professionally a couple months ago and intentionally try to use only the necessary pressure to make a chord sound right.

Though the progress is much more difficult and slower than expected, I'm still playing.

I am 36 just learning to play bass.

It was either learn a new language or learn music.

Just got a Fender American Elite P/J bass after playing a borrowed Rickenbacker.  I'm in love.

I have Lupus which causes my my hands to be pretty stiff just like RA and has destroyed the distal joint in my right index (why is stopped playing bass) but playing guitar has really helped so maybe will for you too.  Concentrating on learning the intro to Texas Flood now.  Not all that hard if you leave out all the.....no, it's pretty challenging no matter what .

I played on and off 15 years ago and quit.  I got good enough to make people who can't play a guitar think I was good.  I quit playing and I'm 45 now and started again a couple weeks ago.  I'm struggling with solos and anything moderately fast.  I'll learn alot of riffs, but never put them together into a whole song.  YouTube vids really help alot.  Didn't have YouTube when I first started playing.