Okay first off, I personally wouldn't recommend the yogurt, dairy products aren't the best for cats, as it can cause diarrhea. Purina one is okay, but there are better food's out there, however you will feed your cat what you feel is best
As for scratching, I would recommend "soft paws" alot of people use them and they work great. I've never personally used them on my cats, because I've always trained them with a spray bottle
We have always had a small spray water filled with water and everytime the cat began to scratch the furniture, rugs, etc. We would tell them no and spray them. They now know what the spray bottle means
All of our cats are a year or older, and we have no problems at all with them scratching where their not supposed to anymore.
As for cat wanting to follow you outdoors, keep an eye on that, because cat's can be sneeky and quick. I would suggest keeping your cat indoors for the most part, however there are other's that believe there is nothing wrong with an indoor/outdoor cat. Ours go outside on the patio where they can't go any further (it is just how our house is set up).
Since your cat is 5 months old, I might suggest to look into spaying her as well, some cats will begin to go into heat between 5-7 months old. We've had one cat go into heat at 5 months old, and another didn't until she was 9 months (we had to wait to spay her because we were in transition of moving).
As for posting pics, you can either use the thumbnail attachment, by using the advance posting option, and scrolling towards the bottom where it says manage attachments, you can upload a pic to a photo host and then use the [*img] [*/img] tags w/out the * or you can sign up for a supporting membership which includes image hosting through PT.