How can I open a Inventor file in older Versions?

1: One way is to save the files in older version
2: To save the files in an neutral system, STEP, SAT

I'm have the same problem whit the versions and it's a pain in the a**. I' think that the file should keep the version of inventor that was created with. I have a big assy created with 2015. We opened in 2016 once and now I'm not able to open it in 2015 again! Aghhh

Of course you can always upgrade your Inventor...

May this be the Best!!

I thought it was a marketing ploy by Autodesk at first. Not having access to files created in the next version of the software? We've been working with AutoCAD for years and it plays well with it's upgrades, or it did until Autodesk rewrote the ubiquitous .dwg. Now you have a three year window of compatibility with AutoCAD. Anyway, it's the fault of the tools used in creating the model. Newer versions implement newer tools. These tools have a mathematical language written into the modeling file. Old versions of Inventor can't read the files because they don't have the tools used to create the features and therefore lack the "language" to translate them. Simply put.

It is simple, just did it now.
Step1: Go to export
Step2: Click on CAD Format
Step3: under the "save as type", select STEP files.
Step4: Click save.

This is how to save in STEP format in a more recent version.
Now you can open this STEP file in an older version.

Step1: Right click on the file
Step2: Select "open with"
Step3: Select "Inventor" i.e. the older version you want to open it with
If its not there in the option, select "more apps" (if you are using windows 10) and select inventor.
Still not there?
Now select "look for another app on this PC"
Then open the Autodesk folder and select the folder for the version you want to open with. Then, open "Bin", scroll down till you see "Inventor" (with the inventor logo), double click it and your file will open.

But the constraints in the drawing will be gone.

Hope this helps?

The Ultimate solution Exist "BUT", takes some time...

Step 1 Save as.step or igs format... Yes, yes, I am aware as you already aware that you will you loose everything (Features & Constrains).

Step 2 To recover the features Follow that link
(http://labs.autodesk.com/utilities/feature_recognition/)
To recover Constrains ??? well... I mean...
...Come on Constrains was never a big issue ;P

- To save files in older version I cannot see how this think can been done!!!

@Driton Don't get me wrong but Inventor is not Autocad and if there is a way to save files in older versions I really want to know...!!!!

All you need do is to click on the topmost left hand side file icon, a dialog box appears,
click on open and locate the old file to be loaded, double click on the old file.
An infomation dialog box appears confirming change in inventor file openning,
click on "accept" and the file will be modified to the recent version.