里 vs 里边 vs 里面 vs 里头（近义词）

1)All the four nouns mean"within a certain space or time".里 is an agglutinative word and the other three are free words.里 is the most commonly used,里面 is a bit literary,and 里头 is the most colloquial.
2)In examples①and②，used after nouns of place or time,the four words are interchangeable.
3)In example③里 cannot be used,because it is an agglutinative word.In④里边，etc.function independently as the subject,indicating 里边 of the refrigerator,cupboard,kitchen,etc.which the speaker already knows and 里 cannot be used.
4)Sometimes 里边，etc.indicate a certain unit,or personage:
5)In examples⑤and⑥里 cannot be used.
6)But 这 or 那 can take 里 or 里边，etc.(这里 and 那里 are already words):