RealVirtual I.O Digital Twin Professional version 6 vs 6.3

Dear,

I purchased and am currently using RealVirtual I.O Digital Twin Professional version 6.

Recently, when I tried to update my Unity project to version 6.3, 

I discovered that RealVirtual I.O Digital Twin Professional version 6.3 must be purchased separately.

I have two questions.

1) Do users who purchased RealVirtual I.O Digital Twin Professional 6.0 have to pay to purchase version 6.3 again?

(Is there no policy for upgrade costs rather than new purchases?)

2) Could you please tell me the key feature differences between RealVirtual I.O Digital Twin Professional 6.0 and 6.3?

Thanks.

Best regards,

Seokhyun Lee