You can enter all information for leagues BLS-2017. When you get your codes for the PRO version, simply change the registration to reflect the new code (as well as the product name and serial number), and upon successful registration, the same software will function as PRO as opposed to STD. The temporary code should work for 5 days regardless. Even if the temp gave you issues last year, try it this year as there are always improvements in the software season to season as well as during the season.
In the e-mail you receive with codes, you can copy that portion which is the registration info in that e-mail. That is, everything between the spaced hyphenated lines. Select that block with your mouse and copy it, then in BLS' registration screen, under "Registration Options" you can select "Paste from Clipboard" and everything will be entered without having to type anything.
You will still want to update BLS-2017 to its most current version, but that is the only purpose of re-downloading. The PRO code simply unlocks PRO features in the same software.
Your upgrade next season to BLS-2018 will be a PRO version and the cost of that upgrade will be the same as the upgrade fee for STD to STD. In short, you will always be a PRO user as long as you upgrade each season.
Always check, download, and install the most recent update of your software to ensure that issues may have been corrected.