K.H.
You cannot force them to do something until they are confident with it. If the 13 month old does not feel confident/comfortable on her feet then no she won't walk , 12 months is a guideline for walking , my 2 girls started walking at 16 months & 18 months , my son walked at 10 months.
The 3 yr sounds like she is getting there with the potty , she does at least go some on the potty , I wouldn't get into the habit of giving candy as a way to get her to go as she will start to expect it , instead use words of encouragment , jump up & down cheering and clapping when she goes if you have to!....you'll be surprised how much kids respond to words and reactions , my son absolutely beams when we tell him how proud we are when he has been trying really hard with things.