sorry that I'm brand new to Xcode so I might not be asking the question correctly.
My goal is to duplicate an iPhone app (a server based game) to be able to run two apps with two different accounts at the same time. I thought it should work similarly like Facebook++, or instagram++.
I followed the procedure from here and I went ahead and opened the Info.plist file using Xcode, and changed the 'Bundle Identifier'. However as I upload my new .ipa file using Cydia Impactor, the app gets uploaded fine, but instantly crashes upon entering.
What am I doing wrong here? Do I need to change any other values? Thanks in advance!
It's very unlikely bundle id is the cause here. You can set it to any value you want. It pretty much doesn't matter for iOS. Only time it matters is when you're trying to install two apps with the same bundle id.
I suggest you check crash report and device logs to find out the cause. You might be messing up entitlements when resigning the app.
The way that Cydia Impactor works is it takes your Apple ID and uses it to resign the given application. Otherwise you wouldn't be able to change its contents. Many applications have multiple entitlements that you have to preserve to order for it to work correctly. Looking at what Cydia Impactor does, it doesn't do it properly. Even the most basic things are ignored. But to do it properly requires pretty complicated logic, so I'm not that surprised.
Some entitlements are required in order for app to work and explicitly crash the application. For example, SiriKit. When an app tries to request permission for it from the user iOS will crash the app if it doesn't have the entitlement. Cydia Impactor ignores this entitlement even though it does create app ID and provisioning profile when resigning. The same goes for keychain groups, app groups and pretty much all entitlements. Cydia Impactor messes up all of them.