Yes, a word for an inanimate object can have a plural form and a plural possessive form; for example:
The plural possessive for "key" is "keys'".
It is the singular possessive form of the noun coaster (inanimate possessive). Example: The coaster's cork bottom became stuck to the table.
No, the word its is a singular pronoun, the possessive form of "it". The plural form of the possessive pronoun "its" is theirs.The plural form of the possessive adjective "its" is their.
Your is the possessive form for a singular or plural noun and a subject or object noun.
Singular possessive: secretary's Plural: secretaries Plural possessive: secretaries'
doors' e.g.: in the house, all the doors' hinges need to be greased. But I would still contest the need to use the possessive for door (inanimate) - in the example above, I feel it is better as "...the hinges of all the doors..."
The plural is relatives. The plural possessive is relatives'.
The plural is lads. The plural possessive is lads'.
The plural form is echoes. The plural possessive is echoes'.
The plural form is suffixes. The plural possessive is suffixes'.
The plural form is Mexicans. The plural possessive is Mexicans'.
The plural form is stepsisters. The plural possessive is stepsisters'.