There's a right way, and a wrong way...

Correct:

if (version <= OLD_VERSION) {
... do_something_old ...
}
else { ... something new ... }

The wrong way:

if (version = NEW_VERSION) {
... do something new ...
} else { ... do something old ... }

What my standup report is today:
I'm modifying thousands of lines of SQL code because the script was hard-coded to only work on SQL Server 2008 R2, and we're using SQL 2017 in our test environment. All of those lines now fail because we don't match your "new version" number.