@Arafat ,
Firstly, let's clean up the English.
"When questioned by the committee, (COMMA) he retracted his previous claim ."
or
"When questioned by the committee, (COMMA) he retracted all OF his previous claimS ."
"So the both 2 sentences…": 'both' = two; so why do you write 'both 2'?
"So both sentences HAVE omitted the " be " verb, (comma) which should be added before "prove " and " questioned". I can see this is convenient in spoken English , but how about IN formal writing ?"
We need to include 'to be' in sentences where we wish to avoid ambiguity. Look at these sentences, and say what the difference is:
"Most Americans consider Beverly Hills, a ritzy suburb to the north of Los Angeles, a desirable place to live."
"Most Americans consider Beverly Hills, a ritzy suburb to the north of Los Angeles, to be a desirable place to live."
(You post your reply, I'll respond).
The two (FULL) forms of your second sentence are:
"When HE WAS questioned by the committee, he retracted his previous claim ." (Passive Voice, Past Tense)
When HE WAS BEING questioned by the committee, he retracted all of his previous claims ." (Passive Voice, Past Progressive Tense)