Is it allowed by Jewish Law to castrate cat (her or him)?

i know that having sex/babies is a mitzvah and its very spiritual... so are you allowed to have sex without any reason... just for fun?

Are jews allowed to get tattoos? I always heard that getting one was not allowed then one time and only one time heard to the contrary.

I am presenting my neice with her tallis at her Bat Mitzvah. Is there a particular prayer I should recite?

From what date in Jewish history did it become the practice to write G-d's name as a double yud? Is the extra yud in the word "yehudim" in the Megilla meant to be an allusion to G-d's name or is there another meaning for the unusual spelling? Kind regards E Sher Cape Town, South Africa