can Catholics wear the sign of David Cross?
No. Many Catholics wear a cross on their rosaries, but most Christians do not wear a cross at all.
Yes.
Jews would probably not be offended by catholics wearing a mezuza. A Jew would not wear a Mezuza, since it's place is in the entrance to a domicile (on the right). Most probably a Jew would be amused by the ignorance of the catholic in using the Mezuza as a pendant, and attribute it to a lack of knowledge, or a misguided belief in spiritualism.
Sure. You can wear as many as you want.
I wouldn't be and I'm from Jordan.
the religion where they wear the inverted crosses is the one related to belief in the anti-christ.
Crosses, I would imagine.
Some religions wear crosses as jewelery, or as clothing (eg., crosses on T'shirts). Jews sometimes wear prayer shawls called "Tallit".
You can do whatever you want.
No. Jehovah's Witnesses do not wear crosses which they view as symbols of pagan worship.
Normal clothes.