Help again!

Set your InDesign document size to [ 5-1/2" x 8-1/2" ] or [ 4-1/4" x 11" ] and insert 24 'facing' pages. [The layout should look like this.] Ask the printer how they want the job provided. Most will probably ask for single page PDFs.

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[Question 1] All you have to do is specify what you want to the printer. In this case it's a 24-page saddle stitch booklet - finish size [ 5-1/2" x 8-1/2" ] or [ 4-1/4" x 11" ]. They'll know what to do with the job from there.

[Question 2] With so few sheets [six] you won't have very much 'stepping' of the inner folded pages if this is printed as a sheet fed job.

Depending on the press run the printer may very well print this on a web press. In which case they'll take care of the folding on press and run the job through a saddle stitcher which will take care of the final 'FLUSH' trimming.

If this is a small press run done as a sheet feed job in six runs with no bleed then they may use 8-1/2" x 11" sheets. In this case I'd specify you'd like a final flush trim on the face after bindery to remove any stepping of interior pages.

Ultimately it's best to discuss your requests with the end printer. The way they decide to print the project can differ from printer to printer and it effects how the job is setup.

One final bit of advice... when you scream for "Help!" and people take time out of their busy day to give you feedback it's only right to post a quick thank you. Otherwise you'll be seen as a jerk and no one will offer to help you in the future.