Are these questions for real coz of late I see a lot of them makes me think they are nothing but a point (XPS) making scheme. If you want to learn, get down to it learn there is no need to keep asking about c or whatever, just start learning and the rest will fit in.
Yes, you can. But most employers want an ios developer who knows obj c as well as it would be useful in maintaining old code. Most ios apps are in objective C. Also learning Objective-C gives you advantage over other swift programmers and makes learning swift easier. So ny advice is if you choose ios development as a career learn both the same way android devs learn Java before Kotlin. It's just my opinion though and remember that swift is completely independent