Children do not understand the concept of "stealing" so instead of dealing with this situation using your anger, it is better to sit with your child and make him/her understand why they should not be doing this.
Shouting only makes matters worse, be it you or your child.
It becomes a little awkward to explain such things to your child.
Children lie when they feel they actions will not be accepted by their parents. Assure your child that you will be there to support them when things go downhill.
Even your child is aware that hitting is not the right thing. You just need to pin point the problem and solve it.
It's normal for kids to get cranky but as a parent do not lose the cool.
All humans are stubborn, more or less. That does not mean you cannot teach your child to put their foot down and patiently listen to what the other person has to say.
When a toddler asks you a question, either it comes out of curiosity or it could be just attention seeking. Whatever is the case, it is always best to feed your child's curiosity and give them undivided attention.
A regular habit or not, thumb sucking can cause problems in a child's speech.