[Closed] Sorry - 10 speed questions??

I have seen the thread regarding bashrings etc. and I am just in the process of building a new bike - for now (the next few weeks) it will be 3x9, until I can afford the 10 speed stuff, but I have a few questions:

1. If I run 2x10, do I 'have' to use a 2x10 shifter? I figure that it shouldn't really matter whether it's 2x10 specific or a 3x10 shifter and not using the last selection? Is this right?

2. I have a 10 speed front mech and I assume I can just adjust the limit screws to stop it wanting to go higher when I convert over the 2x10 rather than the current 3x9.

3. What are people finding the best combination is for the number of teeth on chainrings & number of teeth on the rear cassette for 2x10?

Sorry if this has been done before.

Thanks all.