Do you mean that plant right in the middle of the tank? I'm not too sure from the picture and was trying to figure that out too.
It almost reminds me of Rotala najean, but I can't tell without a closer picture of it. There are others here that are better at plant ID's than me though, so maybe they can chime in. You can cut the hygro whereever you want. If you leave the bottom part of the cutting in, it will branch out from where you cut it. IME pennywort doesn't stay low, so I don't think you'll have much luck with it wrapping around the front. At least not if it's Hydrocotyle leucocephala. There are a few species that stay low though. Verticellata is one of them I think and there is at least one more, but I can't remember the name.