Show me a way for downgrade clx PLC

Hi all,
A few years before, I've upgraded a clx 1756 L61 cpu from v13 to v15. Today I want to downgrade it v13 again. But at this period I've made many modifications and additions to program. So I can't load original v13 backup. When I want to downgrade the program from change cpu menu I see only v15 and v16 options. Can you show me a way to downgrade it again please?

Thank you...

My two guesses are:

1. You do not have RSLogix 5000 v13 installed on the computer you are using to edit the program. Each major revision of RSLogix 5000 needs to be installed separately.

2. You have used features in the program that are available in v15 but not in v13.

My guess is that you're trying to revert to v13 so you can use obsolete 1756-L1 controllers. I can't think of another reason not to stay with a stable release of v15 firmware if that's what you are already running.