Hi there I thought I would jump in here a touch as you are on the right track but there are some glaring points that need to be cleared up for you before you go and purchase flooring. Laminate flooring is a Hi Def image of Timber flooring/oak/Natural Species etc and then transposed using a heat method to a MDF or HDF core, then profiled with a click system for ease of installation, maintenance relocation and repair. Good laminate flooring (Quikstep or Krono Swiss) can be very rewarding , look very much like natural timber, and be very durable against scratching and indentation. Laminates nemesis is high saturation of water or moisture. Good e budget solution for all living areas and rooms except toilets bathroom or laundrys. Engineered boards are a veneer of Natural timber and are just as durable as the solid version of whatever species you choose. Whether that be Spotted Gum, Jarrah or Oak. Sorry but you CAN re sand engineered boards. When re sanding occurs through a professional sander, the top .5mm is the depth of the product that you generally ever really need to remove. Some engineered flooring has a 6mm wear layer/ veneer and that's more than if you purchased a solid 19mm raw timber floor. Engineered boards are less likely "cup"(edge of the boards rising so that you can see a little lip) than a solid. We would recommend that if you are considering a timber floor please consult a retailer that only handles timber and specializes in that medium. Hope this helped

R u laying boards over the concrete or beside?

Me too. I think you would not get a close enough match to your floor and then it would stand out. Looks good as you have done it

The knots look like pine to me. Is that raw timber or does it have a coating? A trip with the pic to the timber shop would be a good bet.