How many active objects do you have in your game?

I would like to ask how many active objects should we have in our window? For iphone4 / samsung s3 I limit my objects (objectcount) to less than 20 (solid objects) or else it will have a really low frame rate. When I create and destroy objects on demand i can notice a lag or a skip. If i make the objects to have physics behavior it will be much worst. Any suggestions or techniques for handling a lot of objects for low performance platforms? I am already using tilebackground / tilemap.

Depends on what you mean by active objects..

Are they moving, do they have transparacy, are there events performed on them every tick, How big are the images, how many collision-points do they have, are they instances of the same object or different objects alltogether?

This topic might help with optimizing:

https://www.scirra.com/tutorials/298/pe ... bile-games

But there are many more tips and tricks scattered over the forum and tutorial-section.