extending cabels

Hi, I have moved into a flat 3 floors above the ground floor and have an intercom if someone wants to enter the property. This cable runs across the floor (I think it used to be pinned to the skirting board) through 3 rooms to the intercom phone. I want to hid this cable under the floorboards...

We are converting out garage into a living space. There are six sockets around waist level where bench once sat. We need to lower the sockets only a couple of feet lower. Would it be better to strip all the wiring and insert new runs (Means ceiling out and replace) or would solder/crimp and heat...