Who is "they"? The company is owned by its shareholders. You will still get the TRW cash dividends, although 18.3% indirectly through SIAF and another 18.3% directly through the TRW (dividend) shares you own.
That's the whole point. Not saying this is a reason, but it could be. By giving up majority control, they can ask a higher price for the pre-IPO shares. Potentially. In the end it's all about creating shareholder value.
No, 36.6%. Which is a minority interest already. SIAF is not doing the IPO. TRW is an independent company, doing their own listing/IPO.