Hi,

Questions on licensing are best directed to Sage Software.

But I can answer the technical question, no:

Sage 50 will convert data from 2015.1 to 2015.2 or 2015.3 or 2016, as long as the 'Edition' of the newer program is the same, or 'higher'.

Editions can be converted from First Step to Pro or Premium or Quantum, as long as the version is the same, or higher.

[email protected] said:

I purchased a 2 user licence of Sage 50 Premium 2015 but in the mean time she's been using the Sage 50 First Step 2016  version.

So it won't be possible, because the software can't convert 2016 data to 2015.   It would convert from First Step 2016 if you updated to the 2016 or newer version of sage 50 Premium, but you won't be able to convert back again.

[email protected] said:

Is it possible for her to install and use my second Premium version licence

Sage 50 won't allow installation of different Editions of the same year.   Your two software packages are from different years, so they can be installed on the same workstation / laptop, however you would have to set up the books over again (export the lists and import them into the other software) and re-enter the transactions and beginning balances) or just update to the 2017 software.