Intention when making tayammum

Q:

1. Is niyyah necessary for tayamum?

2. Do I have to specify that I am doing tayamum for wudhu or for ghusal?

3. Do I have to specify that I am doing tayamum for a specific reason i.e for praying salaah, for janaazah, etc.?

4. If I do tayamum for janaazah, can I pray salaah with that tayamum?

5. Is tayamum valid without niyyah?

Husband telling wife "Pack your bags and leave"

Q: I would like to enquire about the validity of my nikaah. My husband and I are experiencing marital difficulties and he has asked me to pack my bags and leave twice this month.

I heard the fact that he asked me to pack my bags and leave even once, it counts as divorce and nikaah needs to be made again after iddah period. Please advise if the nikaah is now invalid.