The Open at launch option defines which web pages iCab should open when launched. The old session can be restored (i.e. all tabs that were open when exiting are opened again), or only the homepage, the quick starter or a blank page can be opened.
This option is evaluated each time the app is started or activated.
The option Open address from clipboard allows iCab to check whether there is a URL in the clipboard when launched. If so, iCab can offer to open this address. This makes it easier if you copy addresses from other apps and want to open them in iCab, as you don't have to paste the address into the address bar manually.
The option Open Tabs for URLs received from other Apps determines whether addresses that are received from other apps are opened in the current tab or in new tabs
Handoff is a feature of iOS and macOS and allows to continue a session of an app on another iPhone, iPad or Mac. If you activate this option, you can transfer the tabs from iCab Mobile on another iOS device to iCab Mobile, and also on the Mac to iCab, and vice versa.