1) why do we pour water from becher into wine bottle before kiddush?
First let’s explain that one must rinse out a Kos before using it for Kiddush. The Gemora in Pesachim explains 10 things relevant to a Kos, some of which are meakev. Rinsing inside and out, shtifa and hadocha, are required. Usually some water is left in the Kos rather than emptying it all out after the Rinsing.
One reason was given, in case the wine in the bottle is pogum, since adding water to pogum wine allows us to use it for Kiddush. Pogum wine cannot be used for Kiddush.
A second reason is that, kabbolistically, the wine represents Din as it is usually red, and water represents rachamim. We want to be mamtik the din with chessed and rachamim so we add some water from the Kos to the wine.
Added bonus questions:
How many segulos for Parnossa or hatzlocha do we find in the Mishna Berura, which is a halocha sefer?