Not sure I've seen a construct2/3 game with reverse time.
So you may have to be the maverik on this one!
The only real way to find out about performance is to make a test engine yourself.
Sure there will be some trade off between how much and how often you record the data and performance
but it may not be that bad especially if it is just position data.
I think you may be complicating things by including physics as at the end of the rewind you would have to re implement whatever physics were present but still should be doable.
Ideally you want to record every frame so I would start from there.
If that is too much then maybe try 1/30 times per second with interpolation as newt as suggested
As for learning arrays, they are not the scary monsters that they seem.
Just visualize a spreadsheet which you can add and retrieve data from.
there are only a handful of construct actions that you need to understand to do this.
For starting off, (just to understand) I would suggest simple test platformer (without physics)
Then just make a 2 x 120 array (this will give you two seconds of rewind)
and every frame populate the array with the x y position of the player sprite.
probably use the push pop method for this.
push adds the latest value to the top moving everything down and pop removes the oldest value from the bottom so the array does not keep growing.
that is the easy bit.
the fiddly bit will be writing the events for rewind to read the array from the bottom to the top and apply them to the player sprite
but still shouldn't be that complicated.
But yea would love to see reverse time in action in a C2/3 game.
I hope you give it a shot.
PS. Im at work so cant make examples, but if I have the time during the week evenings I may try something cant promise though.
(edit) now that Im thinking about it you may have to make the recording interval separate from frame rate and probably will need to have to smoothly move between the points if it reversing with slowdown. But anyway start with the simple example above to kick off the learning process.