How do I determine if a score is acceptable for handicap purposes?

What makes a golf score acceptable for handicap purposes? A score qualifies for handicap purposes when it meets all five requirements listed below — covering format of play, companionship, adherence to the Rules of Golf, course rating status, and active season conditions.

A score is acceptable for handicap purposes if the round has been played:

In an authorized format of play (see Rule 2.1a) over at least the minimum number of holes required for either a 9-hole or an 18-hole score to be acceptable (see Rule 2.2),
In the company of at least one other person who may also act as a marker, provided all other relevant requirements of the Rules of Golf are satisfied,
By the Rules of Golf (see Rule 2.1b),
On a golf course with a current Course Rating and Slope Rating, where length and normal playing difficulty are maintained at a consistent level (see Appendix G),
On a golf course during its active season (i.e., the period designated by the relevant golf association or club during which the course is open for normal play and handicap scores may be submitted — see Appendix G).

If one or more of the requirements set out above is not met, the score is not acceptable for handicap purposes. (Rule 2.1, Rules of Handicapping)