Analysis - continue game vs CPU from given point...?

Hi all - just started playing on Chess.com again using the mobile app (iPhone) - this might be the wrong place to ask, and it's likely also covered elsewhere but not been able to find.... does anyone know if it's possible to continue a game vs the CPU from any given point...?
I often go through the analysis steps, and like that you can trail through the alternative suggestions - but often I would like to just try a different move and then play the CPU.
Also - I guess there is that slightly annoying feeling when you have skewered your opponent and they resign before you can really get stuck in (I know it's fair enough to do, but I do sometimes think some people resign at the first slightest advantage - and I quite like the end game - whether in front or not)....