The necklace first. With a lobster catch like that it is not going to be very old - I would be guessing 1970's on. Actually jewellery like this is still being made today. The metal work has been given an "antique" finish - not to deceive, but because antique style jewellery is considered attractive. When you say "clean" - do you mean the stones or the metal work? If the stones are secure in their setting, a brush with a dampened toothbrush is not going to hurt. If the stones have open backs, and are very grubby, you could try a drop of washing up liquid in the water you moisten the brush brush with. If you mean the metal chain, unless it is rusty or something, I would guess it is meant to look that way. Always dry costume jewellery very thoroughly after cleaning it - use a hair dryer on a low setting.
The pendant I would guess is Bohemian / Czech 1930's though it is often hard to judge from a photo (see remarks about "antique style" above.) The use of filigree metal work and coloured rhinestones is very typical. It seems to me there may be something stamped on the pendant loop? Sadly if it missing 2 coloured rhinestones it is of little value - I have many craft boxes full of rhinestones of different shapes and sizes - it is rare you are able to find one matching replacement, let alone 2.
