Ownership is a fundamental concept in property law which can be difficult to apply to software, such as computer games.
A physical record of information, such as a game disc, a piece of paper with a product key on it, or a computer hard drive with software installed on it, is personal property (chattels). You own these things. However, copyright law restricts what you can legally do with them.
For example, the copyright holder generally has the exclusive right to make a copy of a program, which would generally include downloading (and saving) a game ISO. In recent decades, anti-circumvention provisions have been added to national copyright laws. These generally make it illegal to use cracks and other techniques for circumventing DRM, even if you “own” a copy of the software.
What is “owned” is the right to assert a claim in court (a chose in action), which is also a kind of property. Specifically, the right to use proprietary software, or software license, is generally understood as a bundle of contractual rights, often documented in an end user license agreement. (While these contractual rights are a kind of property that can be owned, “ownership” of software can also refer to the rights of the copyright holder, which the more limited rights of a licensee are derived from.)
Actually determining the legal effect of a software license is complex. As it is intended to create contractual rights, the terms of the contract (license agreement) are important, but not determinative. Consumer law may impose standard “fair dealing” terms which could have complex effects on the rights associated with a digital product in a particular jurisdiction. Because of the low money value involved, these complex legal issues are rarely tested in court.
The specific questions you pose all appear to breach copyright or anti-circumvention law. However, you may have acquired contractual rights, including implied rights associated with your purchase of chattels, or dealings with a platform operator like Steam, which limit the copyright holder’s ability to take action against you. You may also have the right to do things that fall within a fair use or fair dealing exception in your jurisdiction.
Again, the law is often untested, especially outside of the United States, because it is rarely in the parties’ interest to litigate. However, the exceptions to anti-circumvention law are often different to, and less permissive than, the exceptions to copyright. To further research your questions in a particular jurisdiction, I would look for exceptions to copyright and anti-circumvention law which protect consumers’ rights, if any, to back up or resell copies of licensed software.