My Sagittaria was small when I initially planted them in the mid/fore ground area. Now their leaves have touched the top and are 12 inches in height.
I already have Giant Sags and Vallisneria planted in the background which have shed their old leaves and are now looking like fore ground plants but over a period of time they will grow tall

So I need to answer some questions so that I dont do anything silly.

1) Can I just cut/pluck the whole Sagittaria leaf till the bottom ? If all the leaves are tall I cant cut all of them
2) Should I trim by cutting it half way ? If I trim Halfway the leaf will eventually turn yellow and die.
3) Is replanting ok by moving it to the background or will the leaves start to die once moved ?