The purpose of purdah

Q: What is termed as Pardah ? Nowadays we see many women making pardah but the cloaks and dress that they wear are colourful and have many designs. Is this permissible? Please explain what is Pardah? Also mention quran and hadith stating pardah and the harms and punishment of women not observing the proper pardah.

Reciting ربنا و لك الحمد حمدا كثيرا طيبا مباركا فيه in fardh Salaah

Q: Can a person read the following Dua in his Fard Salaah:  حمدا كثيرا طيبا مباركا فيه after reading: ربنا و لك الحمد, in ruku', similarly can he read in jalsah: اللهم اغفرلي و ارحمني و عافني و اجبرني و ارزقني and if he is a muqtadi can he read these two dua's?

Giving zakaat in lieu of a service

Q: I am living with my children in my parents house in Pakistan and my husband is away in another country. The maid in my parents house helps me with house hold work. I give her some money every month which is from my zakat. I told her about that and she is happy to accept the zakaat money and help me with house hold work. My mother pays her regular salary on top of that. My question is will that money be accepted as zakaat?