Can I choose my backup date
Can I backup data from a old iPhone
Yes.
You only have one backup for a device, unless you have taken an archive of the previous backups on iTunes. Every time you take a backup the data is overwritten (Added/Deleted) based on the data on the iPhone. This is true for both iCloud and iTunes.
In other words, your backup has the same data as that of your device at the time the backup was taken.