Newbee I2C questions

Question #1: Can I used (both) two I2C buses (B6 B7) & (B7 B8) ?

Yes, but you'll have to use I2C1.setup to set up I2C each time you want to use the other bus (I guess you mean you mean B6/B7 + B8/B9).

I'd strongly recommend that you just use I2c2 on B10 and B11.

I2C Class shows instances of I2C1,I2C2&I2C3

I2C3 is for other chips/boards that have it - the Espruino board doesn't.

software rejects using I2C2 but likes only I2C1?

Do you have an example of what doesn't work? I2c2 definitely should be fine.

The Espruino board layout pins only shows "same" I2C1 on both pins (B6 B7) and (B8 B9)?

It can be on B6/B7 or B8/B9 and is configurable by I2C1.setup - but it can't be on both at the same time, and it can't be on B6/B9 (for instance)