SSD and HDD os combinations

[BadNight]

This is the scenario:
-I have a 1tb hdd. It's split into 4 partitions.
-I get a ssd that's nowhere near 1tb. Can I just clone only the os partition and still boot fine?
-If it were to work, would I be able to boot with both drives installed? Will it screw up the drive letters/shortcuts to programs? Or will the os on the hdd just be labeled as some unused letter?
-If that worked, what if I don't delete the original os off the hdd, could I just keep booting it that way? Just in case the ssd failed for whatever reason, could I just plug the hdd to it's original sata location and boot up like nothing happened?

 

[ArtPog]

If one of the partitions on the 1 TB HDD contains the OS you can clone that partition over to the SSD. We're assuming of course that the disk-space capacity of the SSD is sufficient to contain that OS partition.

After a successful partition-cloning operation, disconnect the HDD from the system and boot only to the SSD as the only disk connected. Assuming the SSD boots and properly functions, then you can reconnect the HDD. Ensure your boot priority order indicates a first boot to the SSD.

Work with the system for a time to determine all is well before deleting the OS files from the HDD if that's what you want. It's not necessary to do this but it's OK if you do.

The likelihood is you will not have to change any drive letters on the HDD but in certain instances that possibility exists.

 

[USAFRet]

Assuming the clone operation from the HDD partition to the SSD works properly, the only issue might be swapping around drive letters.

For example:
Currently, you have 4 partitions on the HDD
P1-C, P2-D, P3-E, P4-F.

Moving the OS over to the SSD, and plugging in the HDD with the same 4 partitions probably gives you this by default:
C - SSD
HDD partitions:
P1-D, P2-E, P3-F, P4-G.

If you have anything relying on those original drive letters, you'll just need to simply swap drive letters around for the partitions.
Thusly:
P1-Y, P2-D, P3-E,P4-F
Now we have the old OS partition as Y (or some random letter), and the other 3 what they used to be.

 

[BadNight]

If you have anything relying on those original drive letters, you'll just need to simply swap drive letters around for the partitions.
Thusly:
P1-Y, P2-D, P3-E,P4-F
Now we have the old OS partition as Y (or some random letter), and the other 3 what they used to be.

This only applies to the original hard drive right? Or would I have to do the same to all other hard drives attached as well?

 

[USAFRet]

If you have anything relying on those original drive letters, you'll just need to simply swap drive letters around for the partitions.
Thusly:
P1-Y, P2-D, P3-E,P4-F
Now we have the old OS partition as Y (or some random letter), and the other 3 what they used to be.

This only applies to the original hard drive right? Or would I have to do the same to all other hard drives attached as well?

Probably only applies to the single drive where you have the OS partition and whatever else.
Can you post a screencap of your Disk Management window? From there, we could make a more certain recommendation of how to proceed.