1)It splits easily. ALL brittle hardwood does. Staples can cause tongue splits easier but many, including myself, have successfully stapled down exotic solids.
2) NOFMA states 3/4" OSB (if it is OSB and not something else) can be used as an acceptable subfloor. Plywood is better but OSB will work.
3) How red is too red?
B. Cherry will develope into a deep redish brown. It is attractive and most like it. It is not fire engine red.
4) Yes, No, and Yes.
5)???? Do you mean the expansion gap suggested at the walls? 3/4" is overkill, IMO. If it is a large area, undercut the sheetrock and use a 1/2" expansion. Then you'll have a 1" expansion space but you don't really need it.