Tier 4 dependent switch to Tier 2 Gen in UK

My wife is in UK on a Tier 4 general student visa. I am working on a Tier 2 ICT visa(issued in Jan 2011). I got a job offer in UK but cannot apply for Tier 2 general visa from within UK as I need to travel back home due to completion of my current assignment. I have some questions in this regard.

1. Can I apply for Tier 4 dependent visa and accept the job offer.
2. Once in UK can I switch to Tier 2 gen visa from Tier 4 dependent visa. Or
3. Can I apply for a Tier 2 Gen visa with the COS issued to me in UK.

Please suggest me the best way to handle this.

Thanks.

Can anyone please help me with this.