As per Valentin, after making few changes this is the code which seems to work fine.

while read line;
do
    day="$(echo $line | awk '{for (i=1; i<=NF; i++) { if($i == "R") { print i - 2; exit} } }')"
    if [[ ${#day} -lt 2 ]]; then day="0${day}"; fi
    month=`date '+%m'`
    year=`date '+%Y'`
    date=`echo $month/$day/$year`
    result=$(sudo /usr/openv/netbackup/bin/admincmd/bpimagelist -client "$(echo $line | awk '{print $1}')" -policy "$(echo $line | awk '{print $2}')" -hoursago 100000 -U | awk -v date="$date" '$1 == date' | wc -l)
    if [[ $result -ne 0 ]];
    then
        echo $line | sed 's/ R / L /'
    else
        echo $line | awk '{
                            afterR=0;
                            for (i=1; i<=NF; i++){
                              if ($i == "R") {
                                $i = "F";
                                afterR=1;
                              }
                              if (afterR == 1 && $i == "O") {
                                $i = "F"
                              }
                            }
                            print $0
                          }'
    fi
done < temp

However one small query is that it should perform these changes only when R is followed by O and until it finds anything but O.

meaning it shouldn't perform any changes if the input file is like

XYZ 123 S S R O O O O

which means R is continued by only O so no need to perform any changes, else anything other than O is found perform the changes

I have a file

XYZ 123 S S R O O S F
PQR 456 F S S R O F F
ABC 789 F S R S S F S

Now in entire row when I find "R" && then "O" or "S" I want to get the column no and based on the column no I need to perform a command and if it's true then display L instead of R and O or S if false then F instead of R and F instead of O(for all consecutive O's) or S

lets say command output is

XYZ is false
PQR is true
ABC is true

then the ouput should be

XYZ 123 S S F F F S F
PQR 456 F S S L O F F
ABC 789 F S L S S F S

I have a file

XYZ 123 S S R O O S F
PQR 456 F S S R O F F
ABC 789 F S R S S F S

Now in entire row when I find "R" && then "O" or "S" I want to get the column no and based on the column no I need to perform a command and if it's true then display L instead of R and O or S if false then F instead of R and F instead of O(for all consecutive O's) or S

now from the column no I will determine date,

let say for 1st row R is on 5 so the date will be column no - 3 i.e 2nd,

for 2nd row date will be 6-3 i.e 3rd, 3rd row again 5-3 i.e 2nd,

So i will be using a variable date=%m/d(from column no-3)/%Y

now the command is ./bpimagelist -client <column 1> -policy <column 2> -hoursago 100000 -U | awk -v date="$date" '$1 == date' | wc -l, now if the value is 0 then it's false if it's gt 0 then it's true.

XYZ is false
PQR is true
ABC is true

then the ouput should be

XYZ 123 S S F F F S F
PQR 456 F S S L O F F
ABC 789 F S L S S F S