H1B Transfer before Oct1 ?

Yes, they need to file an H1b visa petition for you.

Is an EAD (i765) tied specifically to my Visa?

Generally an EAD let's you work anywhere, but there are some cases where that is not true such as a student on a STEM extension.

I130 petition. my mother is a permanent resident and wan to file i130 for my divorced brother. he is in usa with out status.

Normally it will not cause him to be put in removal proceedings, however he cannot get the visa without leaving the U.S.

I want to hire an immigrant worker whom is here on a work visa with another company. Do I need to do anything to change his visa

Probably an H2, so you will need alien certification with the Department of Labor, and then you can file the visa petition for him.

Can employers refuse to show the I-9 record of their past employees when asked by immigration officials?

If they are audited, they must comply and show their records.

When applying as sponsor for immigration... Is the amount of dependants based on what you claim for the year on your taxes?

It is based on what you mark on the tax return.

Yes.

F2B I-130 got approved Jan,2008 does my son who was born Nov, 1991(now 21) is eligible to move with me?

F2b for August 2013 is at December 1, 2005, so the visa is not yet available.

Need advice on my partner who is travelling to the US after recent rejection from the UK.

Generally UK nationals can come to the U.S. as Visa Waivers. They can stay 90 days.

Not at all likely.