Yes. Most 1 year olds are babbling and have a few words sometime (mama, dada, and a few others). In my experience, it is very common for babies not to be talking too much at 1 year.
Yes. Every baby develops at a different pace and that's ok. Most babies by 12 months are babbling, understand their name and some may have a few words. It's helpful to have an understanding of when certain developmental milestones can occur. The CDC has a great list at: http://www.Cdc.Gov/ncbddd/actearly/milestones/milestones-1yr.Html if you're concerned, speak to your pediatrician.
Yes. As long as you mean not speaking in sentences, it is normal. A 1 year old should say "mama" and "papa" specifically, plus at least one other word. If s/he has no sounds that seem to be words, that is not normal. More significant would be whether your child responds to his/her name and seems to hear. Any concerns warrant a visit to your pediatrician, and possibly audiology testing.
Yes. It is not out of the realm of normal, especially if there is more than one language being spoken in your home. Most kids do have just a few words by 12 months, though they are usually only understandable to the parent. However, it is worth discussing your concerns with the pediatrician to make sure there are no other problems that might interfere with language development.
Yes. Only if a 1 year old baby had been developing in a normal sequence (smiling ... Laughing/squealing ... Babbling ... Making simple syllable sounds ... ) would it be ok to not talk by age 1. Such a baby would be expected to start saying "dada" or "baba" next, and then "mama", at 12-15 months. The baby must also be normal in motor skills and interpersonal activities, or a problem might exist.
Yes. Not everyone thinks of talking like pediatricians do. If your child can say mamma and dadda and get it right then he is doing well.