Do I need an extra accessory to mount it on the ceiling? If so, is SGR-HP-P600X01 compatible with this 90x60 cm version?

A 36-month / 3-year or 48-month / 4-year warranty refers to the total duration of the warranty from the date of receiving the goods. Compared to standard statutory rights, this gives you an additional 12 months / 1 year or 24 months / 2 years, respectively, to file a claim.
Specifications can be changed without notice. Images are for illustrative purposes only.