Hy friends
iam new in the programming apple world but i have for my first project problems to build the app.
The problem is that my customer give me project files which are coded for 2 years with IOS SDK 8.0 i have at the moment
on my mac sdk 10.2.1 i think .
Is it possible to change the base sdk back to 8.0 ?
Not in that example, no.
The usual process in that case is to lower the '[ <target>General/Deployment Info ]Deployment Target' - just be aware your code may need updating as well.
Otherwise, if you must stay at 8.x iOS, install an older Xcode, such as 6.2, (where a need to submit to the store using iOS 10.x would be set aside), but that may only present different issues, requiring you to learn outdated code, processes etc. - my advice is to modernize now, instead.
No, it's not practical to change back to the 8.0 SDK. You'll need to update the project to 10.2 for submission to the app store, anyway.
If you run in to a situation where you have to have an older version of Xcode, they're all available for download from Apple at developer.apple.com/download.