Hi
I'm a professional photographer wishing to learn how to assemble time-lapse clips. I will use them on my own social media and possibly for a client whose instagram I look after. I have also just started recording the pictures for a one-year time lapse project for the same client: the final assembly of this film will not be until next year. For now, I just wish to learn the software and share any successful results. Can I buy private license now and upgrade when necessary? Many thanks for help! Looking forward to joining the LR Timelapse community :-)

Yes, you can buy private now and later the "Crossgrade" to Pro, see: https://lrtimelapse.com/upgrade/
Check out the license terms: https://lrtimelapse.com/eula/ to learn about the limit up to which you are allowed to use the private license commercially.
You can find the differences between the features here:
https://lrtimelapse.com/features/

Many thanks :-)