I have to fetch the data from multiple tables separately from BigQuery into same dataframe using python in local laptop

Sure, you can use an f-string here to just insert so to say your table name into the query

import os
import pandas as pd
from google.cloud import bigquery
os.environ["GOOGLE_APPLICATION_CREDENTIALS"]="C:/Users/GA/credentials.json"

client = bigquery.Client()
dflist = []

QUERY = (
    """
    SELECT 
    fullVisitorId,
    visitNumber,
    visitId,
    visitStartTime,
    date,
    totals.bounces,
    totals.hits,
    totals.newVisits,
    totals.pageviews,
    totals.screenviews,
    totals.sessionQualityDim,
    totals.timeOnScreen,
    totals.timeOnSite,
    totals.totalTransactionRevenue,
    totals.transactionRevenue,
    totals.transactions
FROM 
    bigquery-public-data:google_analytics_sample.ga_sessions_{date}
    order by fullVisitorId, date, visitNumber, hitNumber
    """
    )

def query_data(date_:str) -> pd.DataFrame:  
    query_job = client.query(QUERY.format(date=date_)) 
    query_result = query_job.result()
    return query_result.to_dataframe()

dates = ["2021", "2022", ...]

finaldf = pd.concat((query_data(date) for date in dates),axis = 0)

note that you don't have to explicitly pass the client and the query to the function as it can just use them from the surrounding scope.