If you want to install Flash on iPhone 4, there is Flash version available to install on iPhone 4 named as Frash by the author Comex. Lets see how to install Flash (Frash) on iPhone 4.
NOTE: Your iPhone must be jailbroken already, and try it at your own risk.
Install Flash on iPhone 4
Open Cydia on you iPhone, Tap “Manage” tab, Tap “Source” button.
Tap “Edit” button on top right, tap “Add” button and enter the following repo URL
http://repo.benm.at/ and tap “Add Source” button.
After adding source, tap the big “return to Cydia” button at the bottom and then “Done” button.
Tap “Search” tab and type “Frash” in the search box. Tap Frash search result and install it.
You may notice Frash Toggle in search results, using this you can enable/disable Frash via SBsettings toggle button.