I can't update to iOS5 because the iPhone 3G doesn't support it. The last iOS update made for this phone was 4.2.1, which is the one I have.. :/
I'm not sure what syncing an iPhone is or how it can be done. Concerning the memory capacity, I have 5.4GB
free out of 6.9GB, so it's far from being full.
I have restarted my device plenty of times. Sometimes quitting the game for a few minutes helps a little but after a while the problems return. The Pet Shop Story game doesn't give me so many problems, not even close. These are the two Story games I play. I wouldn't care so much if I didn't have 60+ neighbors, but as a 4-star player, I tip daily and freezing for 20+ seconds every time I visit a restaurant, and freezing whenever I leave a tip on a table, it becomes really frustrating. Sometimes the game shuts itself down on its own and makes my home screen (springboard) very slow and keeps freezing for a few seconds.
I have other games installed on my phone and they never caused me any problems :/
And thank you for your help.