Returns a batch of the learner's saved words for practice, ten by default, for the meaning, writing, listening or speaking skills. selection: recommended (default) returns due practice first (early steps, then the most overdue reviews), then writing, listening or speaking for words already in progress (writing only after a meaning was answered correctly), then the newest words only when nothing is due; due returns only practice due now; new returns words not yet practised in the requested skills; all ignores scheduling. Each item includes the word, its meanings and examples, practiceTargets naming the skill and meaning to practise next, and speechUrl when saved pronunciation audio exists. The returned practiceId identifies the batch for submit_training_results, and practiceGuidance states Polidict's exercise and saving rules. Read-only; an empty list means no suitable words. timezone is an IANA name; when omitted, dates use UTC.