Answers

We like to use a sanded caulk that matches the grout for that seam between the countertop and backsplash. The flexibility of the caulk allows it to expand and contract without cracking out like normal grout. It's not a forever fix and needs to be touched up occasionaly, but it's a much better solution than just grouting that joint.

I would suggest calling the original installer and let them buff it out. 

The trick with caulking is to spray the wet caulking with Windex and then tool it with your finger.  For "rookies" you may want to use masking tape.  Here is a YouTube video that might help, too. https://www.youtube.com/watch?v=uPGKdwnHhaE

First, clean out the existing caulk the best you can with a utility knife, flat razor or a putty knife.  To get it extra clean and depending on what type of caulk was there before, you can use baking soda and a rag to remove hard water build up and caulk residue.  Once you've done that, I recommend GE Silicone 2 or Dap Kitchen and bath caulk.  (I like the small hand tubes, not the kind that goes in a gun.)  Water based caulks are easier to work with, but silicone has it's advantages.  To apply silicone, clean and dry the area, apply a small bead, then spray the area with soapy water.  This will keep the silicone from spreading up the edge of the splash or onto the counter.  Then wipe once with your finger and your done.  The waterbased caulk can be applied in a small bead and then cleaned up/smoothed with a wet rag.

I would call a local company that sells quartz countertops and find a service rep that can come out and handle the repair properly. This will ensure that it is repaired by a professional. First I would call the company that installed the countertop and they may be able to take care of it for you or point you in right direction.

The process of repairing quartz countertop problems and blemishes is a very special skill that involves complicated processes. The painstaking task often requires painting and chip repair so you should never try to fix blemished pieces on your own. In fact, you should leave all of your installation and repair to professionals. If you try to fix them yourself you will doubtlessly be creating more problems for yourself down the road. This can be an expensive and annoying mistake if you constantly have to repair a wrongly installed countertop.

We keep a spray bottle filled with the solution below on the counter and use it as needed. We apply sealer once a year.

•1/2 cup rubbing alcohol
•2 cups water
•8 drops dawn dish soap

Using warm soapy water is the best for daily cleaning.  There are many granite cleaners on the market that will help you if you really want to scrub and bring back that original shine.  Laticrete (formerly DuPont) stone care products are great.  They make a revitilizer spray that is excellent for weekly cleaning.  It has a bit of sealer in it as well, so it will help keep those tops shiny.

Warm soappy water! Cleaning products takes away your granite sealer.

We use and reccommend TS&G Disinfectant & Cleaner. It is made by MIRACLE Sealants Company and you can use it safely on Tile, Stone, & Grout. It kills Molds & Mildew, Disinfects, Bacterial, Fungicidal, Cleanses, Deoderizes, & Eliminates Oders.