about relaive clause

[alan]

I have read some materials about relative clause stating that

if it's a defining clause ,then the relative pronoun (who,which,etc.)can be changed into participle...that is

e.g. the man who works here is my dad=
the man working here is my dad

but for a non defining clause ,the relative pronoun must remain in the sentence and never use participle to replace it..

is that rule true for all cases ?? if that is the case...Is the following sentence considered to be right :

e.g. this stone,which weighs 1kg,is of great value=
this stone,weighing 1kg,is of great value?????

Another question is ..for non definingclause....the relative pronoun used must be WHOM instead of WHO ,is that right ?

e.g. i have 3 sisters,all of whom are living in abc town.(but not who)

thanks for answering me these 2 questions which confuse me for a long time

[Casiopea]

[1] This stone, weighing 1kg, is of great value.
=> The stone is valuable, no matter how much it weighs.

[2] The stone weighing 1kg is of great value.
=> The stone is valuable because it weighs 1kg.

[3] The stone - the one weighing 1kg - is of great value.
=> Mid-way through the sentence, the speaker inserts an afterthought. It's valuable because it weighs 1kg.

[4] I have 3 sisters, all of whom are living in abc town.
=> In that context, 'whom' functions as the object of the preposition 'of'.

Note, many speakers today omit -m on 'whom',

EX: all of who are . . . (how speakers use language)
EX: all of whom are . . . (how language works)

[alan]

thank you so much !!!

[Casiopea]

You're welcome.