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Fix the 2x2 to the wall and rest the bath on it. Not sure if you have batons that replace the 2x2 provided by the manufacturer, I've never had any come with a bath.
It's just that people started to install them with the legs only and they need to be stuck solid to the wall and have something to rest on.
It does depend on the household but you could be supporting quite a bit of weight and it's not unheard of for 2 people to be quite active in a bath so it needs good support.
CT1 is an adhesive sealant and you need that there to protect the wall when the decorative sealant between tiles and bathtop stops working. That way in the future you just replace the decorative sealant.
Airhead
hvsds
as in under the lip at the top of the bath? if so, it appears to have come prepared as there’s batons of sorts around the perimeter already :)